Returns the plan optimization strategy of a SQL statement.
EXPLANATION( string-expression [ cursor-type ], [update-status ] )
string-expression The SQL statement, which is commonly a SELECT statement, but can also be an UPDATE or DELETE statement.
cursor-type A cursor type, expressed as a string. Possible values are asensitive, insensitive, sensitive, or keyset-driven. If cursor-type is not specified, asensitive is used by default.
update-status A string parameter accepting one of the following values indicating how the optimizer should treat the given cursor:
|READ-ONLY||The cursor is read-only.|
|READ-WRITE (default)||The cursor can be read or written to.|
|FOR UPDATE||The cursor can be read or written to. This is the same as READ-WRITE.|
The optimization is returned as a string.
This information can help you decide which indexes to add or how to structure your database for better performance.
SQL/2003 Vendor extension.
The following statement passes a SELECT statement as a string parameter and returns the plan for executing the query.
SELECT EXPLANATION( 'SELECT * FROM Departments WHERE DepartmentID > 100' );
The following statement returns a string containing the short form of the text plan for an INSENSITIVE cursor over the query 'select * from Departments where ....'.
SELECT EXPLANATION( 'SELECT * FROM Departments WHERE DepartmentID > 100', 'insensitive', 'read-only' );
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