14 The ORACLE_LOADER Access Driver

FIXED length

The FIXED clause is used to identify the records as all having a fixed size of length bytes. The size specified for FIXED records must include any record termination characters, such as newlines. Compared to other record types, fixed-length fields in fixed-length records are the easiest field and record formats for the access driver to process.

The following is an example of using FIXED records. It assumes there is a 1-byte newline character at the end of each record in the datafile. It is followed by a sample of the datafile that can be used to load it.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (RECORDS FIXED 20 FIELDS (first_name CHAR(7),
                                                                    last_name CHAR(8),
                                                                    year_of_birth CHAR(4)))
                         LOCATION ('info.dat'));

Alvin  Tolliver1976
KennethBaer    1963
Mary   Dube    1973

VARIABLE size

The VARIABLE clause is used to indicate that the records have a variable length and that each record is preceded by a character string containing a number with the count of bytes for the record. The length of the character string containing the count field is the size argument that follows the VARIABLE parameter. Note that size indicates a count of bytes, not characters. The count at the beginning of the record must include any record termination characters, but it does not include the size of the count field itself. The number of bytes in the record termination characters can vary depending on how the file is created and on what platform it is created.

The following is an example of using VARIABLE records. It assumes there is a 1-byte newline character at the end of each record in the datafile. It is followed by a sample of the datafile that can be used to load it.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (RECORDS VARIABLE 2 FIELDS TERMINATED BY ','
                                             (first_name CHAR(7),
                                              last_name CHAR(8),
                                              year_of_birth CHAR(4)))
                         LOCATION ('info.dat'));

21Alvin,Tolliver,1976,
19Kenneth,Baer,1963,
16Mary,Dube,1973,

DELIMITED BY

The DELIMITED BY clause is used to indicate the characters that identify the end of a record.

If DELIMITED BY NEWLINE is specified, then the actual value used is platform-specific. On UNIX platforms, NEWLINE is assumed to be "\n". On Windows NT, NEWLINE is assumed to be "\r\n".

If DELIMITED BY string is specified, string can be either text or a series of hexadecimal digits enclosed within quotation marks and prefixed by OX or X. If it is text, then the text is converted to the character set of the datafile and the result is used for identifying record boundaries. See string.

If the following conditions are true, then you must use hexadecimal digits to identify the delimiter:

• The character set of the access parameters is different from the character set of the datafile.

• Some characters in the delimiter string cannot be translated into the character set of the datafile.

The hexadecimal digits are converted into bytes, and there is no character set translation performed on the hexadecimal string.

If the end of the file is found before the record terminator, the access driver proceeds as if a terminator was found, and all unprocessed data up to the end of the file is considered part of the record.

The following is an example of using DELIMITED BY records.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (RECORDS DELIMITED BY '|' FIELDS TERMINATED BY ','
                                              (first_name CHAR(7),
                                               last_name CHAR(8),
                                               year_of_birth CHAR(4)))
                         LOCATION ('info.dat'));

Alvin,Tolliver,1976|Kenneth,Baer,1963|Mary,Dube,1973

CHARACTERSET

The CHARACTERSET string clause identifies the character set of the datafile. If a character set is not specified, the data is assumed to be in the default character set for the database. See string.

PREPROCESSOR

If the file you want to load contains data records that are not in a format supported by the ORACLE_LOADER access driver, use the PREPROCESSOR clause to specify a user-supplied preprocessor program that will execute for every data file. Note that the program specification must be enclosed in a shell script if it uses arguments (see the description of file_spec).

The preprocessor program converts the data to a record format supported by the access driver and then writes the converted record data to standard output (stdout), which the access driver reads as input. The syntax of the PREPROCESSOR clause is as follows:

directory_spec

Specifies the directory object containing the name of the preprocessor program to execute for every data file. If directory_spec is omitted, then the default directory specified for the external table is used. The user accessing the external table must have the EXECUTE privilege for the directory object that is used.

The preprocessor program must reside in a directory object, so that access to it can be controlled for security reasons. The OS system manager must create a directory corresponding to the directory object and must verify that OS-user ORACLE has access to that directory. DBAs must ensure that only approved users are allowed access to the directory object associated with the directory path. Although multiple database users can have access to a directory object, only those with the EXECUTE privilege can run a preprocessor in that directory. No existing database user with read-write privileges to a directory object will be able to use the preprocessing feature. DBAs can prevent preprocessors from ever being used by never granting the EXECUTE privilege to anyone for a directory object.

file_spec

The name of the preprocessor program. It is appended to the path name associated with the directory object that is being used (either the directory_spec or the default directory for the external table). The file_spec cannot contain an absolute or relative directory path.

If the preprocessor program requires any arguments (for example, gunzip -c), then you must specify the program name and its arguments in an executable shell script (or on Windows systems, in a batch (.bat) file). The shell script must reside in directory_spec. Keep the following in mind when you create a shell script for use with the PREPROCESSOR clause:

• The full path name must be specified for system commands such as gunzip.

• The preprocessor shell script must have EXECUTE permissions

• The data file listed in the external table LOCATION clause should be referred to by $1. (On Windows systems, the LOCATION clause should be referred to by %1.)

• On Windows systems, the first line in the .bat file must be the following:

  @echo off
  

  Otherwise, by default, Windows will echo the contents of the batch file (which will be treated as input by the external table access driver).

See Example 14-2 for an example of using a shell script.

It is important to verify that the correct version of the preprocessor program is in the operating system directory.

Example 14-1 shows a sample use of the PREPROCESSOR clause when creating an external table. Note that the preprocessor file is in a separate directory from the data files and log files.

SQL> CREATE TABLE xtab (recno varchar2(2000))
     2    ORGANIZATION EXTERNAL (
     3    TYPE ORACLE_LOADER
     4    DEFAULT DIRECTORY data_dir
     5    ACCESS PARAMETERS (
     6    RECORDS DELIMITED BY NEWLINE
     7    PREPROCESSOR execdir:'zcat'
     8    FIELDS (recno char(2000)))
     9    LOCATION ('foo.dat.gz'))
   10    REJECT LIMIT UNLIMITED;
Table created.

Example 14-2 shows how to specify a shell script on the PREPROCESSOR clause when creating an external table.

SQL> CREATE TABLE xtab (recno varchar2(2000))
     2    ORGANIZATION EXTERNAL (
     3    TYPE ORACLE_LOADER
     4    DEFAULT DIRECTORY data_dir
     5    ACCESS PARAMETERS (
     6    RECORDS DELIMITED BY NEWLINE
     7    PREPROCESSOR execdir:'uncompress.sh'
     8    FIELDS (recno char(2000)))
     9    LOCATION ('foo.dat.gz'))
   10    REJECT LIMIT UNLIMITED;
Table created.

LANGUAGE

The LANGUAGE clause allows you to specify a language name (for example, FRENCH), from which locale-sensitive information about the data can be derived. The following are some examples the type of information that can be derived from the language name:

• Day and month names and their abbreviations

• Symbols for equivalent expressions for A.M., P.M., A.D., and B.C.

• Default sorting sequence for character data when the ORDER BY SQL clause is specified

• Writing direction (right to left or left to right)

• Affirmative and negative response strings (for example, YES and NO)

TERRITORY

The TERRITORY clause allows you to specify a territory name to further determine input data characteristics. For example, in some countries a decimal point is used in numbers rather than a comma (for example, 531.298 instead of 531,298).

DATA IS...ENDIAN

The DATA IS...ENDIAN clause indicates the endianness of data whose byte order may vary depending on the platform that generated the datafile. Fields of the following types are affected by this clause:

• INTEGER

• UNSIGNED INTEGER

• FLOAT

• BINARY_FLOAT

• DOUBLE

• BINARY_DOUBLE

• VARCHAR (numeric count only)

• VARRAW (numeric count only)

• Any character datatype in the UTF16 character set

• Any string specified by RECORDS DELIMITED BY string and in the UTF16 character set

A common platform that generates little-endian data is Windows NT. Big-endian platforms include Sun Solaris and IBM MVS. If the DATA IS...ENDIAN clause is not specified, then the data is assumed to have the same endianness as the platform where the access driver is running. UTF-16 datafiles may have a mark at the beginning of the file indicating the endianness of the data. This mark will override the DATA IS...ENDIAN clause.

BYTEORDERMARK (CHECK | NOCHECK)

The BYTEORDERMARK clause is used to specify whether the datafile should be checked for the presence of a byte-order mark (BOM). This clause is meaningful only when the character set is Unicode.

BYTEORDERMARK NOCHECK indicates that the datafile should not be checked for a BOM and that all the data in the datafile should be read as data.

BYTEORDERMARK CHECK indicates that the datafile should be checked for a BOM. This is the default behavior for a datafile in a Unicode character set.

The following are examples of some possible scenarios:

• If the data is specified as being little or big-endian and CHECK is specified and it is determined that the specified endianness does not match the datafile, then an error is returned. For example, suppose you specify the following:

  DATA IS LITTLE ENDIAN 
  BYTEORDERMARK CHECK 
  

  If the BOM is checked in the Unicode datafile and the data is actually big-endian, an error is returned because you specified little-endian.

• If a BOM is not found and no endianness is specified with the DATA IS...ENDIAN parameter, then the endianness of the platform is used.

• If BYTEORDERMARK NOCHECK is specified and the DATA IS...ENDIAN parameter specified an endianness, then that value is used. Otherwise, the endianness of the platform is used.

  See Also:

  Byte Ordering

STRING SIZES ARE IN

The STRING SIZES ARE IN clause is used to indicate whether the lengths specified for character strings are in bytes or characters. If this clause is not specified, the access driver uses the mode that the database uses. Character types with embedded lengths (such as VARCHAR) are also affected by this clause. If this clause is specified, the embedded lengths are a character count, not a byte count. Specifying STRING SIZES ARE IN CHARACTERS is needed only when loading multibyte character sets, such as UTF16.

LOAD WHEN

The LOAD WHEN condition_spec clause is used to identify the records that should be passed to the database. The evaluation method varies:

• If the condition_spec references a field in the record, the clause is evaluated only after all fields have been parsed from the record, but before any NULLIF or DEFAULTIF clauses have been evaluated.

• If the condition specification references only ranges (and no field names), then the clause is evaluated before the fields are parsed. This is useful for cases where the records in the file that are not to be loaded cannot be parsed into the current record definition without errors.

See condition_spec.

The following are some examples of using LOAD WHEN:

LOAD WHEN (empid != BLANKS)
LOAD WHEN ((dept_id = "SPORTING GOODS" OR dept_id = "SHOES") AND total_sales != 0)

BADFILE | NOBADFILE

The BADFILE clause names the file to which records are written when they cannot be loaded because of errors. For example, a record was written to the bad file because a field in the datafile could not be converted to the datatype of a column in the external table. Records that fail the LOAD WHEN clause are not written to the bad file but are written to the discard file instead. Also, any errors in using a record from an external table (such as a constraint violation when using INSERT INTO...AS SELECT... from an external table) will not cause the record to be written to the bad file.

The purpose of the bad file is to have one file where all rejected data can be examined and fixed so that it can be loaded. If you do not intend to fix the data, then you can use the NOBADFILE option to prevent creation of a bad file, even if there are bad records.

If you specify BADFILE, you must specify a file name or you will receive an error.

If neither BADFILE nor NOBADFILE is specified, the default is to create a bad file if at least one record is rejected. The name of the file will be the table name followed by _%p, and it will have an extension of .bad.

See [directory object name:] filename.

DISCARDFILE | NODISCARDFILE

The DISCARDFILE clause names the file to which records are written that fail the condition in the LOAD WHEN clause. The discard file is created when the first record to be discarded is encountered. If the same external table is accessed multiple times, then the discard file is rewritten each time. If there is no need to save the discarded records in a separate file, then use NODISCARDFILE.

If you specify DISCARDFILE, you must specify a file name or you will receive an error.

If neither DISCARDFILE nor NODISCARDFILE is specified, the default is to create a discard file if at least one record fails the LOAD WHEN clause. The name of the file will be the table name followed by _%p and it will have an extension of .dsc.

See [directory object name:] filename.

LOG FILE | NOLOGFILE

The LOGFILE clause names the file that contains messages generated by the external tables utility while it was accessing data in the datafile. If a log file already exists by the same name, the access driver reopens that log file and appends new log information to the end. This is different from bad files and discard files, which overwrite any existing file. NOLOGFILE is used to prevent creation of a log file.

If you specify LOGFILE, you must specify a file name or you will receive an error.

If neither LOGFILE nor NOLOGFILE is specified, the default is to create a log file. The name of the file will be the table name followed by _%p and it will have an extension of .log.

See [directory object name:] filename.

SKIP

Skips the specified number of records in the datafile before loading. SKIP can be specified only when nonparallel access is being made to the data.

READSIZE

The READSIZE parameter specifies the size of the read buffer used to process records. The size of the read buffer must be at least as big as the largest input record the access driver will encounter. The size is specified with an integer indicating the number of bytes. The default value is 512 KB (524288 bytes). You must specify a larger value if any of the records in the datafile are larger than 512 KB. There is no limit on how large READSIZE can be, but practically, it is limited by the largest amount of memory that can be allocated by the access driver.

The amount of memory available for allocation is another limit because additional buffers might be allocated. The additional buffer is used to correctly complete the processing of any records that may have been split (either in the data; at the delimiter; or if multi character/byte delimiters are used, in the delimiter itself).

DISABLE_DIRECTORY_LINK_CHECK

By default, the ORACLE_LOADER access driver checks before opening data and log files to ensure that the directory being used is not a symbolic link. The DISABLE_DIRECTORY_LINK_CHECK parameter (which takes no arguments) directs the access driver to bypass this check, allowing you to use files for which the parent directory may be a symbolic link.

DATE_CACHE

By default, the date cache feature is enabled (for 1000 elements). To completely disable the date cache feature, set it to 0.

DATE_CACHE specifies the date cache size (in entries). For example, DATE_CACHE=5000 specifies that each date cache created can contain a maximum of 5000 unique date entries. Every table has its own date cache, if one is needed. A date cache is created only if at least one date or timestamp value is loaded that requires datatype conversion in order to be stored in the table.

The date cache feature is enabled by default. The default date cache size is 1000 elements. If the default size is used and the number of unique input values loaded exceeds 1000, then the date cache feature is automatically disabled for that table. However, if you override the default and specify a nonzero date cache size and that size is exceeded, then the cache is not disabled.

You can use the date cache statistics (entries, hits, and misses) contained in the log file to tune the size of the cache for future similar loads.

string

A string is a quoted series of characters or hexadecimal digits. If it is a series of characters, then those characters will be converted into the character set of the data file. If it is a series of hexadecimal digits, then there must be an even number of hexadecimal digits. The hexadecimal digits are converted into their binary translation, and the translation is treated as a character string in the character set of the data file. This means that once the hexadecimal digits have been converted into their binary translation, there is no other character set translation that occurs. The syntax for a string is as follows:

condition_spec

The condition_spec is an expression that evaluates to either true or false. It specifies one or more conditions that are joined by Boolean operators. The conditions and Boolean operators are evaluated from left to right. (Boolean operators are applied after the conditions are evaluated.) Parentheses can be used to override the default order of evaluation of Boolean operators. The evaluation of condition_spec clauses slows record processing, so these clauses should be used sparingly. The syntax for condition_spec is as follows:

Note that if the condition specification contains any conditions that reference field names, then the condition specifications are evaluated only after all fields have been found in the record and after blank trimming has been done. It is not useful to compare a field to BLANKS if blanks have been trimmed from the field.

The following are some examples of using condition_spec:

empid = BLANKS OR last_name = BLANKS
(dept_id = SPORTING GOODS OR dept_id = SHOES) AND total_sales != 0

[directory object name:] filename

This clause is used to specify the name of an output file (BADFILE, DISCARDFILE, or LOGFILE). The directory object name is the name of a directory object where the user accessing the external table has privileges to write. If the directory object name is omitted, then the value specified for the DEFAULT DIRECTORY clause in the CREATE TABLE...ORGANIZATION EXTERNAL statement is used.

The filename parameter is the name of the file to create in the directory object. The access driver does some symbol substitution to help make file names unique in parallel loads. The symbol substitutions supported for UNIX and Windows NT are as follows (other platforms may have different symbols):

• %p is replaced by the process ID of the current process. For example, if the process ID of the access driver is 12345, then exttab_%p.log becomes exttab_12345.log.

• %a is replaced by the agent number of the current process. The agent number is the unique number assigned to each parallel process accessing the external table. This number is padded to the left with zeros to fill three characters. For example, if the third parallel agent is creating a file and bad_data_%a.bad was specified as the file name, then the agent would create a file named bad_data_003.bad.

• %% is replaced by %. If there is a need to have a percent sign in the file name, then this symbol substitution is used.

If the % character is encountered followed by anything other than one of the preceding characters, then an error is returned.

If %p or %a is not used to create unique file names for output files and an external table is being accessed in parallel, then output files may be corrupted or agents may be unable to write to the files.

If you specify BADFILE (or DISCARDFILE or LOGFILE), you must specify a file name for it or you will receive an error. However, if you do not specify BADFILE (or DISCARDFILE or LOGFILE), then the access driver uses the name of the table followed by _%p as the name of the file. If no extension is supplied for the file, a default extension will be used. For bad files, the default extension is .bad; for discard files, the default is .dsc; and for log files, the default is .log.

condition

A condition compares a range of bytes or a field from the record against a constant string. The source of the comparison can be either a field in the record or a byte range in the record. The comparison is done on a byte-by-byte basis. If a string is specified as the target of the comparison, it will be translated into the character set of the datafile. If the field has a noncharacter datatype, no datatype conversion is performed on either the field value or the string. The syntax for a condition is as follows:

empid != BLANKS
10:13 = 0x'00000830'
PRODUCT_COUNT = "MISSING"

delim_spec

The delim_spec clause is used to find the end (and if ENCLOSED BY is specified, the start) of a field. Its syntax is as follows:

If ENCLOSED BY is specified, the access driver starts at the current position in the record and skips over all whitespace looking for the first delimiter. All whitespace between the current position and the first delimiter is ignored. Next, the access driver looks for the second enclosure delimiter (or looks for the first one again if a second one is not specified). Everything between those two delimiters is considered part of the field.

If TERMINATED BY string is specified with the ENCLOSED BY clause, then the terminator string must immediately follow the second enclosure delimiter. Any whitespace between the second enclosure delimiter and the terminating delimiter is skipped. If anything other than whitespace is found between the two delimiters, then the row is rejected for being incorrectly formatted.

If TERMINATED BY is specified without the ENCLOSED BY clause, then everything between the current position in the record and the next occurrence of the termination string is considered part of the field.

If OPTIONALLY is specified, then TERMINATED BY must also be specified. The OPTIONALLY parameter means the ENCLOSED BY delimiters can either both be present or both be absent. The terminating delimiter must be present regardless of whether the ENCLOSED BY delimiters are present. If OPTIONALLY is specified, then the access driver skips over all whitespace, looking for the first nonblank character. Once the first nonblank character is found, the access driver checks to see if the current position contains the first enclosure delimiter. If it does, then the access driver finds the second enclosure string and everything between the first and second enclosure delimiters is considered part of the field. The terminating delimiter must immediately follow the second enclosure delimiter (with optional whitespace allowed between the second enclosure delimiter and the terminating delimiter). If the first enclosure string is not found at the first nonblank character, then the access driver looks for the terminating delimiter. In this case, leading blanks are trimmed.

After the delimiters have been found, the current position in the record is set to the spot after the last delimiter for the field. If TERMINATED BY WHITESPACE was specified, then the current position in the record is set to after all whitespace following the field.

A missing terminator for the last field in the record is not an error. The access driver proceeds as if the terminator was found. It is an error if the second enclosure delimiter is missing.

The string used for the second enclosure can be included in the data field by including the second enclosure twice. For example, if a field is enclosed by single quotation marks, a data field could contain a single quotation mark by doing something like the following:

'I don''t like green eggs and ham'

There is no way to quote a terminator string in the field data without using enclosing delimiters. Because the field parser does not look for the terminating delimiter until after it has found the enclosing delimiters, the field can contain the terminating delimiter.

In general, specifying single characters for the strings is faster than multiple characters. Also, searching data in fixed-width character sets is usually faster than searching data in varying-width character sets.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (FIELDS TERMINATED BY WHITESPACE)
                         LOCATION ('info.dat'));

Alvin Tolliver 1976
Kenneth Baer 1963
Mary Dube 1973

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4)) 
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                        ACCESS PARAMETERS (FIELDS TERMINATED BY "," ENCLOSED BY "("  AND ")")
                        LOCATION ('info.dat'));

(Alvin) ,   (Tolliver),(1976)
(Kenneth),  (Baer) ,(1963)
(Mary),(Dube) ,   (1973)

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (FIELDS TERMINATED BY ','
                                            OPTIONALLY ENCLOSED BY '(' and ')'
                                            LRTRIM)
                         LOCATION ('info.dat'));

Alvin ,   Tolliver , 1976
(Kenneth),  (Baer), (1963)
( Mary ), Dube ,    (1973)

trim_spec

The trim_spec clause is used to specify that spaces should be trimmed from the beginning of a text field, the end of a text field, or both. Spaces include blanks and other nonprinting characters such as tabs, line feeds, and carriage returns. The syntax for the trim_spec clause is as follows:

NOTRIM indicates that no characters will be trimmed from the field.

LRTRIM, LTRIM, and RTRIM are used to indicate that characters should be trimmed from the field. LRTRIM means that both leading and trailing spaces are trimmed. LTRIM means that leading spaces will be trimmed. RTRIM means trailing spaces are trimmed.

LDRTRIM is used to provide compatibility with SQL*Loader trim features. It is the same as NOTRIM except in the following cases:

• If the field is not a delimited field, then spaces will be trimmed from the right.

• If the field is a delimited field with OPTIONALLY ENCLOSED BY specified, and the optional enclosures are missing for a particular instance, then spaces will be trimmed from the left.

The default is LDRTRIM. Specifying NOTRIM yields the fastest performance.

The trim_spec clause can be specified before the field list to set the default trimming for all fields. If trim_spec is omitted before the field list, then LDRTRIM is the default trim setting. The default trimming can be overridden for an individual field as part of the datatype_spec.

If trimming is specified for a field that is all spaces, then the field will be set to NULL.

In the following example, all data is fixed-length; however, the character data will not be loaded with leading spaces. The example is followed by a sample of the datafile that can be used to load it.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20),
year_of_birth CHAR(4))
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (FIELDS LTRIM)
                         LOCATION ('info.dat'));

Alvin,           Tolliver,1976
Kenneth,         Baer,    1963
Mary,            Dube,    1973

MISSING FIELD VALUES ARE NULL

MISSING FIELD VALUES ARE NULL indicates that if there is not enough data in a record for all fields, then those fields with missing data values are set to NULL. If MISSING FIELD VALUES ARE NULL is not specified, and there is not enough data in the record for all fields, then the row is rejected.

In the following example, the second record is stored with a NULL set for the year_of_birth column, even though the data for the year of birth is missing from the datafile. If the MISSING FIELD VALUES ARE NULL clause was omitted from the access parameters, then the second row would be rejected because it did not have a value for the year_of_birth column. The example is followed by a sample of the datafile that can be used to load it.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth INT)
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (FIELDS TERMINATED BY ","
                                            MISSING FIELD VALUES ARE NULL)
                         LOCATION ('info.dat'));
 
Alvin,Tolliver,1976
Baer,Kenneth
Mary,Dube,1973

field_list

The field_list clause identifies the fields in the datafile and their datatypes. Evaluation criteria for the field_list clause are as follows:

• If no datatype is specified for a field, it is assumed to be CHAR(1) for a nondelimited field, and CHAR(255)for a delimited field.

• If no field list is specified, then the fields in the datafile are assumed to be in the same order as the fields in the external table. The datatype for all fields is CHAR(255) unless the column in the database is CHAR or VARCHAR. If the column in the database is CHAR or VARCHAR, then the datatype for the field is still CHAR but the length is either 255 or the length of the column, whichever is greater.

• If no field list is specified and no delim_spec clause is specified, then the fields in the datafile are assumed to be in the same order as fields in the external table. All fields are assumed to be CHAR(255) and terminated by a comma.

This example shows the definition for an external table with no field_list and a delim_spec. It is followed by a sample of the datafile that can be used to load it.

CREATE TABLE emp_load (first_name CHAR(15), last_name CHAR(20), year_of_birth INT)
  ORGANIZATION EXTERNAL (TYPE ORACLE_LOADER DEFAULT DIRECTORY ext_tab_dir
                         ACCESS PARAMETERS (FIELDS TERMINATED BY "|")
                         LOCATION ('info.dat'));

Alvin|Tolliver|1976
Kenneth|Baer|1963
Mary|Dube|1973

The syntax for the field_list clause is as follows:

field_name

The field_name is a string identifying the name of a field in the datafile. If the string is not within quotation marks, the name is uppercased when matching field names with column names in the external table.

If field_name matches the name of a column in the external table that is referenced in the query, then the field value is used for the value of that external table column. If the name does not match any referenced name in the external table, then the field is not loaded but can be used for clause evaluation (for example WHEN or NULLIF).

pos_spec

The pos_spec clause indicates the position of the column within the record. For a full description of the syntax, see pos_spec Clause.

datatype_spec

The datatype_spec clause indicates the datatype of the field. If datatype_spec is omitted, the access driver assumes the datatype is CHAR(255). For a full description of the syntax, see datatype_spec Clause.

init_spec

The init_spec clause indicates when a field is NULL or has a default value. For a full description of the syntax, see init_spec Clause.

pos_spec Clause

The pos_spec clause indicates the position of the column within the record. The setting of the STRING SIZES ARE IN clause determines whether pos_spec refers to byte positions or character positions. Using character positions with varying-width character sets takes significantly longer than using character positions with fixed-width character sets. Binary and multibyte character data should not be present in the same datafile when pos_spec is used for character positions. If they are, then the results are unpredictable. The syntax for the pos_spec clause is as follows:

CREATE TABLE emp_load (first_name CHAR(15),
                      last_name CHAR(20),
                      year_of_birth INT,
                      phone CHAR(12),
                      area_code CHAR(3),
                      exchange CHAR(3),
                      extension CHAR(4))
  ORGANIZATION EXTERNAL
  (TYPE ORACLE_LOADER
   DEFAULT DIRECTORY ext_tab_dir
   ACCESS PARAMETERS
     (FIELDS RTRIM
            (first_name (1:15) CHAR(15),
             last_name (*:+20),
             year_of_birth (36:39),
             phone (40:52),
             area_code (*-12: +3),
             exchange (*+1: +3),
             extension (*+1: +4)))
   LOCATION ('info.dat'));

Alvin          Tolliver            1976415-922-1982
Kenneth        Baer                1963212-341-7912
Mary           Dube                1973309-672-2341

datatype_spec Clause

The datatype_spec clause is used to describe the datatype of a field in the datafile if the datatype is different than the default. The datatype of the field can be different than the datatype of a corresponding column in the external table. The access driver handles the necessary conversions. The syntax for the datatype_spec clause is as follows:

If the number of bytes or characters in any field is 0, then the field is assumed to be NULL. The optional DEFAULTIF clause specifies when the field is set to its default value. Also, the optional NULLIF clause specifies other conditions for when the column associated with the field is set to NULL. If the DEFAULTIF or NULLIF clause is true, then the actions of those clauses override whatever values are read from the datafile.

SQL> CREATE TABLE emp_load
  2    (employee_number      CHAR(5),
  3     employee_dob         CHAR(20),
  4     employee_last_name   CHAR(20),
  5     employee_first_name  CHAR(15),
  6     employee_middle_name CHAR(15),
  7     employee_hire_date   DATE)
  8  ORGANIZATION EXTERNAL
  9    (TYPE ORACLE_LOADER
 10     DEFAULT DIRECTORY def_dir1
 11     ACCESS PARAMETERS
 12       (RECORDS DELIMITED BY NEWLINE
 13        FIELDS (employee_number      CHAR(2),
 14                employee_dob         CHAR(20),
 15                employee_last_name   CHAR(18),
 16                employee_first_name  CHAR(11),
 17                employee_middle_name CHAR(11),
 18                employee_hire_date   CHAR(10) date_format DATE mask "mm/dd/yyyy"
 19               )
 20       )
 21     LOCATION ('info.dat')
 22    );
 
Table created.

date_format_spec

The date_format_spec clause is used to indicate that a character string field contains date data, time data, or both, in a specific format. This information is used only when a character field is converted to a date or time datatype and only when a character string field is mapped into a date column.

For detailed information about the correct way to specify date and time formats, see Oracle Database SQL Language Reference.

The syntax for the date_format_spec clause is as follows:

Description of the illustration et_dateformat.gif

DATE

The DATE clause indicates that the string contains a date.

MASK

The MASK clause is used to override the default globalization format mask for the datatype. If a date mask is not specified, then the settings of NLS parameters for the database (not the session settings) for the appropriate globalization parameter for the datatype are used. The NLS_DATABASE_PARAMETERS view shows these settings.

• NLS_DATE_FORMAT for DATE datatypes

• NLS_TIMESTAMP_FORMAT for TIMESTAMP datatypes

• NLS_TIMESTAMP_TZ_FORMAT for TIMESTAMP WITH TIME ZONE datatypes

Please note the following:

• The database setting for the NLS_NUMERIC_CHARACTERS initialization parameter (that is, from the NLS_DATABASE_PARAMETERS view) governs the decimal separator for implicit conversion from character to numeric datatypes.

• A group separator is not allowed in the default format.

TIMESTAMP

The TIMESTAMP clause indicates that a field contains a formatted timestamp.

INTERVAL

The INTERVAL clause indicates that a field contains a formatted interval. The type of interval can be either YEAR TO MONTH or DAY TO SECOND.

The following example shows a sample use of a complex DATE character string and a TIMESTAMP character string. It is followed by a sample of the datafile that can be used to load it.

SQL> CREATE TABLE emp_load
  2    (employee_number      CHAR(5),
  3     employee_dob         CHAR(20),
  4     employee_last_name   CHAR(20),
  5     employee_first_name  CHAR(15),
  6     employee_middle_name CHAR(15),
  7     employee_hire_date   DATE,
  8     rec_creation_date    TIMESTAMP WITH TIME ZONE)
  9  ORGANIZATION EXTERNAL
 10    (TYPE ORACLE_LOADER
 11     DEFAULT DIRECTORY def_dir1
 12     ACCESS PARAMETERS
 13       (RECORDS DELIMITED BY NEWLINE
 14        FIELDS (employee_number      CHAR(2),
 15                employee_dob         CHAR(20),
 16                employee_last_name   CHAR(18),
 17                employee_first_name  CHAR(11),
 18                employee_middle_name CHAR(11),
 19                employee_hire_date   CHAR(22) date_format DATE mask "mm/dd/yyyy hh:mi:ss AM",
 20                rec_creation_date    CHAR(35) date_format TIMESTAMP WITH TIME ZONE mask "DD-MON-RR HH.MI.SSXFF AM TZH:TZM"
 21               )
 22       )
 23     LOCATION ('infoc.dat')
 24    );
 
Table created.

SQL> SELECT * FROM emp_load;
 
EMPLO EMPLOYEE_DOB         EMPLOYEE_LAST_NAME   EMPLOYEE_FIRST_ EMPLOYEE_MIDDLE
----- -------------------- -------------------- --------------- ---------------
EMPLOYEE_
---------
REC_CREATION_DATE
---------------------------------------------------------------------------
56    november, 15, 1980   baker                mary            alice
01-SEP-04
01-DEC-04 11.22.03.034567 AM -08:00
 
87    december, 20, 1970   roper                lisa            marie
01-JAN-02
01-DEC-02 02.03.00.678573 AM -08:00
 
 
2 rows selected.

The info.dat file looks like the following. Note that this is 2 long records. There is one space between the data fields (09/01/2004, 01/01/2002) and the time field that follows.

56november, 15, 1980  baker             mary       alice      09/01/2004 08:23:01 AM01-DEC-04 11.22.03.034567 AM -08:00
87december, 20, 1970  roper             lisa       marie      01/01/2002 02:44:55 PM01-DEC-02 02.03.00.678573 AM -08:00

CREATE TABLE emp_load
             (first_name CHAR(15),
              last_name CHAR(20),
              resume CHAR(2000),
              picture RAW(2000))
  ORGANIZATION EXTERNAL
  (TYPE ORACLE_LOADER
   DEFAULT DIRECTORY ext_tab_dir
   ACCESS PARAMETERS
     (RECORDS
        VARIABLE 2
        DATA IS BIG ENDIAN
        CHARACTERSET US7ASCII
      FIELDS (first_name VARCHAR(2,12),
              last_name VARCHAR(2,20),
              resume VARCHAR(4,10000),
              picture VARRAW(4,100000)))
    LOCATION ('info.dat'));

0005Alvin0008Tolliver0000001DAlvin Tolliver's Resume etc. 0000001013f4690a30bc29d7e40023ab4599ffff

CREATE TABLE emp_load
             (first_name CHAR(15),
              last_name CHAR(20),
              resume CHAR(2000),
              picture RAW (2000))
  ORGANIZATION EXTERNAL
  (TYPE ORACLE_LOADER
    DEFAULT DIRECTORY ext_tab_dir
    ACCESS PARAMETERS
      (FIELDS (first_name VARCHARC(5,12),
               last_name VARCHARC(2,20),
               resume VARCHARC(4,10000),
               picture VARRAWC(4,100000)))
  LOCATION ('info.dat'));

00007William05Ricca0035Resume for William Ricca is missing0000

init_spec Clause

The init_spec clause is used to specify when a field should be set to NULL or when it should be set to a default value. The syntax for the init_spec clause is as follows:

Only one NULLIF clause and only one DEFAULTIF clause can be specified for any field. These clauses behave as follows:

• If NULLIF condition_spec is specified and it evaluates to true, the field is set to NULL.

• If DEFAULTIF condition_spec is specified and it evaluates to true, the value of the field is set to a default value. The default value depends on the datatype of the field, as follows:

  • For a character datatype, the default value is an empty string.

  • For a numeric datatype, the default value is a 0.

  • For a date datatype, the default value is NULL.

• If a NULLIF clause and a DEFAULTIF clause are both specified for a field, then the NULLIF clause is evaluated first and the DEFAULTIF clause is evaluated only if the NULLIF clause evaluates to false.

transform

Each transform specified in the transform clause identifies a column in the external table and then a specifies how to calculate the value of the column. The syntax is as follows:

The NULL transform is used to set the external table column to NULL in every row. The CONSTANT transform is used to set the external table column to the same value in every row. The CONCAT transform is used to set the external table column to the concatenation of constant strings and/or fields in the current record from the datafile. The LOBFILE transform is used to load data into a field for a record from another datafile. Each of these transforms is explained further in the following sections.

lobfile_attr_list

The lobfile_attr_list lists additional attributes of the LOBFILE. The syntax is as follows:

Description of the illustration et_lobfile_attr.gif

The FROM clause lists the names of all directory objects that will be used for LOBFILEs. It is used only when a field name is specified for the directory object of the name of the LOBFILE. The purpose of the FROM clause is to determine the type of access allowed to the named directory objects during initialization. If directory object in the value of field is not a directory object in this list, then the row will be rejected.

The CLOB attribute indicates that the data in the LOBFILE is character data (as opposed to RAW data). Character data may need to be translated into the character set used to store the LOB in the database.

The CHARACTERSET attribute contains the name of the character set for the data in the LOBFILEs.

The BLOB attribute indicates that the data in the LOBFILE is raw data.

If neither CLOB nor BLOB is specified, then CLOB is assumed. If no character set is specified for character LOBFILEs, then the character set of the datafile is assumed.