Oracle® TimesTen InMemory Database SQL Reference Release 11.2.1 Part Number E1307003 


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The TT_HASH function returns the hash value of an expression or list of expressions. This value is the value that is used by a hash index.
SQL syntax
TT_HASH(Expression [,...])
Parameters
TT_HASH has the parameter:
Parameter  Description 

Expression [,...] 
One or more expressions to be used to determine the hash value of the expression or list of expressions. 
Description
Each expression must have a known data type and must be nonnullable. The hash value of the expression depends on both the value of the expression and its type. For example, TT_HASH of an TT_INTEGER with value 25 may be different from TT_HASH of a NUMBER or BINARY_DOUBLE with value 25. If you specify a list of expressions, the TT_HASH result depends on the order of the expressions in the list.
Since constants and expressions that are not simple column references are subject to internal typing rules, over which applications have no control, the best way to ensure that TT_HASH computes the desired value for expressions that are not simple column references is to CAST the expression to the desired type.
The result type of TT_HASH is TT_INTEGER in 32bit mode and TT_BIGINT in 64 bit mode.
TT_HASH can be used in a SQL statement anywhere an expression can be used. For example, TT_HASH can be used in a SELECT list, a WHERE or HAVING clause, an ORDER BY clause, or a GROUP BY clause.
The output of error messages, trace messages, and ttAXactAdmin
display the hash value as a signed decimal so that the value matches TT_HASH output.
Examples
The following query finds the set of rows whose primary key columns hash to a given hash value:
SELECT * FROM t1 WHERE TT_HASH(pkey_col1, pkey_col2, pkey_col3) = 12345678;