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Using Parameter Markers

Parameter markers are are usually represented in an SQL statement with a question mark, ? or a string prefixed with a colon, :somename.

Her is an example:

select * from EMP where ENAME = ? or ENAME = ?

Parameter markers are primarily used in prepared SQL statements that will be cached by the database server. The purpose with cached statements is that the database server will analyze the execution plan once when the SQL is first executed. Subsequent invocations of the same SQL will then only replace the parameter markers with appropriate values, which results in much better response than executing SQLs with dynamic values directly in the SQL.

Parameter marker processing is managed by the JDBC driver and not all drivers supports it. One notable example is that the Oracle JDBC driver lacks support completely.

With a JDBC driver that does support parameter marker processing, the following window appears when executing the previous SQL statement.

parameterMarkerSubst

For parameter marker processing to work in the SQL Commander, make sure the SQL->Process Parameter Markers in SQL main menu option is enabled.

To close the window and apply the current values using the keyboard, use the Ctrl+Enter (Command+Enter on Mac OS X) key binding.