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What Is macro ?

Macro :

Macros are SQL statements stored in the Data Directory. 

Collection of statements which does simple tasks. 

A macro can store one or more SQL statements. 

For frequent request we go for it. 

We cannot take procedural control statements in side macro (If-Else,For) 

Only one DDL(Create,Alter,Drop) statement we can take here 

With in macro we can write aDML(SELECT,INSERT,UPDATE,DELETE Statements) 

It takes only input parameters 

All statements inside macro acts like transactions. 

All updates with in a macro are considered a transaction 

If all steps work, all work committed. If a single step fails, all the updated rows are automatically rollback

to their original values prior to the macro executing. 

We execute macro with EXEC command 

It cannot support store procedure language. 

CREATE MACRO : Each SQL statement within a macro must have its ownsemi-colon to help the optimizer delineate one SQL statement from another.All the SQL statements must be enclosed in parentheses to be created and

treated as a single transaction. 

The following syntax for a CREATE MACRO 

CREATE MACRO <macro-name> AS ( [ SELECT........; ] 

[ INSERT........; ] 

[ UPDATE.......; ] 

[ DELETE.........;] ) 

Example : 

CREATE MACRO emp1_m AS 

( UPDATE emp1 SET job='po' WHERE job='clerk'; 

SELECT empno,ename,sal,deptno FROM emp1 WHERE job='po';); 

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 In the above example macro contains two SQL statements:one is UPDATEand other one is SELECT.Both statements are enclosed in the parentheses,each of the statements ends with a semi-colon (;)

The following syntax for a EXECUTE MACRO 

EXEC <macro-name> [ (<Parameter-value-list>) ]; 

or EXECUTE <macro-name> [ (<Parameter-value-list>) ];

The REPLACE MACRO statement is used to modify an existing macro.Itreplaces an existing macro with a new macro, in its entirety. There fore, the

name must be exactly the same.It is very good idea to do a HELP DATABASEbefore replacing a macro. 

The following syntax for REPLACE MACRO 

REPLACE MACRO <macro-name> AS 

( [INSERT ......;] [UPDATE......;] [DELETE.......;] [SELECT ......;] 

); 

Ex: REPLACE MACRO MM AS(SELECT DEPTNO,EMPNO,SAL FROM EMP WHERE

DEPTNO=10;); 

It is the time to execute them. 

DROP MACRO:

The DROP MACRO statement has only one function. It deletes a macroout of the DD. Therefore, it is a very powerful and easy command to use.Additionally, there is no question that asks if you are sure you want toDROP THE MACRO and there is no undo functionality. If a user has theprivilege to DROP a macro and executes a DROP MACRO command, themacro is gone. The following is the syntax of the DROP MACRO command. An example: 

DROP MACRO Myfirst_macro ; 

Unlike the CREATE MACRO that had to establish the parameters andprovide the SQL, the DROP MACRO does not care. The name is all it needsto eliminate the macro from the DD. Since there is no undo function for the DROP MACRO, it is a good idea tohave the CREATE MACRO statement stored somewhere on disk availablefor recovery. If it is not saved at creation, before dropping the macro, aSHOW MACRO can be executed to return the CREATE MACRO statementfor saving on disk. However, if a large macro is being built, it should be

saved initially. Otherwise, if the CREATE MACRO is too large to store inthe DD, part of it may be lost using the SHOW MACRO  

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