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Oracle® Database SQL Language Reference
11g Release 1 (11.1)

Part Number B28286-01
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Description of treat.gif follows
Description of the illustration treat.gif


TREAT changes the declared type of an expression.

You must have the EXECUTE object privilege on type to use this function.

This function does not support CLOB data directly. However, CLOBs can be passed in as arguments through implicit data conversion.

See Also:

"Datatype Comparison Rules" for more information


The following statement uses the table oe.persons, which is created in "Substitutable Table and Column Examples". That table is based on the person_t type, which is created in "Type Hierarchy Example". The example retrieves the salary attribute of all people in the persons table, the value being null for instances of people that are not employees.

SELECT name, TREAT(VALUE(p) AS employee_t).salary salary 
   FROM persons p;

NAME                          SALARY
------------------------- ----------
Joe                           100000
Tim                             1000

You can use the TREAT function to create an index on the subtype attributes of a substitutable column. For an example, see "Indexing on Substitutable Columns: Examples".