For SQL statements that need to be executed many times, it is often beneficial to prepare the SQL statement once, and reuse the query plan by using parameter markers to substitute the input values during runtime.
In DB2 Everyplace, a parameter marker is represented by a "?" character, and indicates where an application variable is to be substituted inside an SQL statement. Parameter markers are referenced by number, and are numbered sequentially from left to right, starting at one. Before the SQL statement is executed, the application must bind a variable storage area to each parameter marker specified in the SQL statement. In addition, the bound variables must be a valid storage area, and must contain input data values when the prepared statement is executed against the database.
The following example illustrates an SQL statement containing two parameter markers.
SELECT * FROM customers WHERE custid = ? AND lastname = ?
Zugehörige Konzepte