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PL/SQL in Scripts
Oracle Tips by Burleson
 

The use of IF-THEN-ELSE logic, looping structures, and other features can make writing a powerful script much simpler. It’s extremely difficult to simulate these logical control structures using only SQL statements.

Anonymous PL/SQL Blocks

Every use of PL/SQL in your script will be done through an anonymous PL/SQL block. Even a call to a stored procedure or function must be executed through an anonymous block. An anonymous PL/SQL block is nothing more than a PL/SQL block that isn’t already compiled in the data dictionary. This is shown in the following example:

DECLARE
   nGPA   number := 0;
 
BEGIN
   SELECT overall_gpa
   INTO   nGPA
   FROM   STUDENTS
   WHERE  ssn = 999999999;
END;

One of the most common uses of anonymous PL/SQL blocks is a call to a stored PL/SQL object, typically for testing purposes.

The exec statement is a quick method to create an anonymous PL/SQL block, but it doesn’t allow you to define any variables. The use of the exec statement is shown in this example, which calls the Annual_Review() procedure.

exec Annual_Review;

If the Annual_Review() procedure required parameters, these would have to be passed as literal values to the procedure. Using exec simply nests the call to the stored object between a BEGIN and an END.

Using DBMS_Output and UTL_File

The DBMS_Output package is often used within anonymous PL/SQL blocks to display the values returned from queries and calls to stored PL/SQL objects. The results of queries inside PL/SQL blocks contained in a script are not spooled to standard output (the terminal or monitor). This package provides a useful method of generating messages that are spooled to standard output. In order to use the DBMS_Output package, you must use the set serveroutput on command at the beginning of your script.

The UTL_File package (introduced with Oracle 7.3) can be used within scripts instead of spooling output to a file with the spool command. The package writes to and reads from files at the operating system level. This package is especially useful if the output of the script needs to be stored in a file.

More information about these packages is provided in Chapter 9.

  
  
This is an excerpt from the book "High Performance Oracle Database Automation" by Jonathan Ingram and Donald K. Burleson, Series Editor.

  
 

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