Performing Essential PL/SQL Tasks

Let’s turn to the highlights of creating, running, deleting, and otherwise managing PL/SQL programs, using SQL*Plus as the front end. Don’t expect to be overwhelmed with detail here; treat this section as a glimpse of topics that will be covered in much greater detail in the chapters ahead.

Creating a Stored Program

To build your own stored PL/SQL program, you use one of SQL’s CREATE statements. For example, if you want to create a stored function named wordcount that counts words in a string, you can do so using a CREATE FUNCTION statement:

CREATE FUNCTION wordcount (str IN VARCHAR2)
   RETURN PLS_INTEGER
AS
   declare local variables go here
BEGIN
   implement algorithm here
END;
/

As with the simple BEGIN-END blocks shown earlier, running this statement from SQL*Plus requires a trailing slash on a line by itself.

Assuming that the database administrator has granted you Oracle’s CREATE PROCEDURE privilege, this statement will cause Oracle to compile and store this stored function in your schema; if your code compiles, you’ll probably see a success message such as:

Function created.

If a table or stored program named wordcount already exists in your Oracle schema, CREATE FUNCTION will fail with the error message ORA-00955: name is already used by an existing object. That is one of the reasons that Oracle provides the OR REPLACE OPTION, which you will want to use probably 99% of the time.

CREATE OR REPLACE FUNCTION wordcount (str IN VARCHAR2) RETURN PLS_INTEGER ...

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