Stored Procedure used in PosgreSQL Professor: Dr. Shu-Ching Chen TA: Hsin-Yu Ha

What are stored procedure A subroutine available to applications that access a relational database system. PL/pgSQL : A loadable procedural language. Creates functions and trigger procedures Adds control structures Performs complex computation Inherits all user-defined types, functions Can be defined to be trusted by the server Easy to use

Why do we need stored procedure Reduce roundtrips across the network Can make security easier to manage Are precompiled One Query Wait, receive, process/compute Database Server Internet

Structure of PL/pgSQL

Declarations (1) Declaring PL/pgSQL variable

Declarations (2) Declaring PL/pgSQL variable and assigning values

Declarations (3) Declaring Function Parameters by using Alias (1) directly give a name to the parameter in the command (2) name ALIAS FOR $n;

Declarations (4) Directly using argument variables

Declarations (5) Attributes %TYPE attribute

Declarations (6) Attributes %ROWTYPE attribute

Comment syntax Single-line comments Block comments

Basic Statements (1) Assignment Executing a Command with NO RESULT – PERFORM

Basic Statements (2) Executing a Command with a Single-row result

Basic Statements (3) Example

Basic Statements (4)

Basic Statements (5) FOUND – Boolean variable

Control Structures(1) RETURN expression

Control Structures(2) IF statements IF … THEN IF … THEN … ELSE IF … THEN … ELSIF … THEN … ELSE

Control Structures(3) CASE statements CASE … WHEN … THEN … ELSE … END CASE CASE WHEN … THEN … ELSE … END CASE

Control Structures(4) LOOP EXIT

Control Structures(5) CONTINUE WHILE

Control Structures(6) FOR (Integer Variant)

Control Structures(7) FOR (Looping through query results)

Control Structures(8) Trapping Errors http://www.postgresql.org/docs/9.1/static/errcodes- appendix.html#ERRCODES-TABLE

Cursors (1) Declaring Cursor Variables OPEN FOR query

Cursors (2) Using Cursors FETCH MOVE NEXT PRIOR FIRST LAST ABSOLUTE count RELATIVE count FORWARD BACKWORD Using Cursors FETCH MOVE

Cursors (3) Using Cursors CLOSE Returning Cursor

Cursors (4) Looping Through a Cursor’s Result

Errors and Messages RAISE Example

Reference PostgreSQL Manuals PostgreSQL 9.1 Practical PostgreSQL http://www.postgresql.org/docs/9.1/static/index.html Practical PostgreSQL http://www.faqs.org/docs/ppbook/c19610.htm