是否可以通过存储过程更改mySql中的表？

Question

here's what I'd like to do in mySQL... I'm getting the feeling that this is simply not feasible, but would love to be wrong...

create procedure foo(IN MYTABLE varchar(50) , IN COLNAME varchar (50), IN MYTYPE varchar(50)) 
begin 
IF (select count(*) from information_schema.columns where table_name =MYTABLE and column_name = COLNAME) = 0 
THEN
alter table MYTABLE add column MYNAME MYTYPE; 
end;

call foo( 'table_foo' , 'column_bar' , 'varchar(100)' );

Answer 1

Don't know why on Earth you would want it, but it's possible:

DELIMITER //
DROP PROCEDURE foo//
CREATE PROCEDURE foo(IN MYTABLE varchar(50) , IN COLNAME varchar (50), IN MYTYPE varchar(50))
BEGIN
  SET @ddl = CONCAT('alter table ', MYTABLE, ' add column (', COLNAME, ' ', MYTYPE, ')');
  PREPARE STMT FROM @ddl;
  EXECUTE STMT;
END;
//

Answer 2

Short answer to why I'd do it.

Updating a deployed database when the version of your schema changes in a released product. Shell scripting is a bad option for cross-platform code so scripting in SQL is great, just remember to drop the procedures after use. If I have deployed 1.1 but am at 1.4 at time of update, i just run the 1.1->1.2, 1.2->1.3, and the 1.3->1.4 scripts in order.