Dynamic SQL:
The Most PL/SQL programs do a predictable, specific job. For illustration, a stored procedure may accept an employee number and salary increase, and then update the sal column in the emp table. In these circumstances, the full text of the UPDATE statement is acknowledged at the compile time. These statements do not change from execution to execution. Therefore, they are known as static SQL statements.
Though, some programs should build and process a variety of the SQL statements at the run time. For illustration, a general-purpose report writer should build various SELECT statements for the various reports it generates. In this situation, the full text of the statement is unknown until the run time. These statements can, and almost certainly will, change from execution to execution. Therefore, they are known as the dynamic SQL statements.
The Dynamic SQL statements are stored in the character strings build by your program at the run time. These strings should contain the text of the valid SQL statement or the PL/SQL block. They can also contain the placeholders for bind arguments. The placeholder is an undeclared identifier, so its name, to which you should prefix a colon, that does not matter. For illustration, the PL/SQL makes no difference between the following strings:
'DELETE FROM emp WHERE sal > :my_sal AND comm < :my_comm'
'DELETE FROM emp WHERE sal > :s AND comm < :c'
To process the most dynamic SQL statements, you can use the EXECUTE IMMEDIATE statement. Though, to process the multi-row query (SELECT statement), you should use the OPEN-FOR, FETCH, and CLOSE statements.