GaussDB(DWS) Stored Procedure Declaration Syntax

Basic Structure

A PL/SQL block can contain a sub-block which can be placed in any section. The following describes the architecture of a PL/SQL block:

• DECLARE: declares variables, types, cursors, and regional stored procedures and functions used in the PL/SQL block.

  DECLARE

  

  This part is optional if no variable needs to be declared.

  • An anonymous block may omit the DECLARE keyword if no variable needs to be declared.
  • For a stored procedure, AS is used, which is equivalent to DECLARE. The AS keyword must be reserved even if there is no variable declaration part.
• EXECUTION: specifies procedure and SQL statements. It is the main part of a program. It is mandatory.

  BEGIN

• EXCEPTION: processes errors. It is optional.

  EXCEPTION

• END

  END;
  /

  

  You are not allowed to use consecutive tabs in the PL/SQL block, because they may result in an exception when the parameter -r is executed using the gsql tool.

PL/SQL Block Classification

PL/SQL blocks are classified into the following types:

• Anonymous block: a dynamic block that can be executed only for once. For details about the syntax, see Anonymous Block.
• Subprogram: a stored procedure, function, operator, or packages stored in a database. A subprogram created in a database can be called by other programs.

Anonymous Block

An anonymous block applies to a script infrequently executed or a one-off activity. An anonymous block is executed in a session and is not stored.

Syntax

Figure 1 shows the syntax diagrams for an anonymous block.

Figure 1 anonymous_block::=

Details about the syntax diagram are as follows:

• The execute part of an anonymous block starts with a BEGIN statement, has a break with an END statement, and ends with a semicolon (;). Type a slash (/) and press Enter to execute the statement.
  

  The terminator "/" must be written in an independent row.

• The declaration section includes the variable definition, type, and cursor definition.
• A simplest anonymous block does not execute any commands. At least one statement, even a null statement, must be presented in any implementation blocks.

Examples

The following lists basic anonymous block programs:

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-- Null statement block:
BEGIN
     NULL; 
END;
/

-- Print information to the console:
BEGIN
     dbms_output.put_line('hello world!'); 
END; 
/

-- Print variable contents to the console:
DECLARE      
     my_var VARCHAR2(30);  
BEGIN      
     my_var :='world';     
     dbms_output.put_line('hello'||my_var); 
END; 
/ 

Subprogram

A subprogram stores stored procedures, functions, operators, and advanced packages. A subprogram created in a database can be called by other programs.