Question

I am trying to write a script that will copy all the data in table a to table b if table a exists. Table b is the exact same structure as table a would be if it exists, though it may not. I am able to copy using the following statement: INSERT INTO 'B' SELECT * FROM 'A', but I don’t know where to use IF EXISTS, or if I even can to determine if I an perform the insertion. I am trying to do this in SQL only as it will be run through as a .sql script from the command line.

Answer 1

MySQL only:

DROP PROCEDURE IF EXISTS myupdate;
DELIMITER //
CREATE PROCEDURE myupdate ()
BEGIN 
DECLARE found VARCHAR(64);
SET found = (SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA = Database() AND TABLE_NAME = 'A');
IF found = 'types' THEN
   INSERT INTO B SELECT * FROM A;
   SELECT 'A into B';
ELSE 
   SELECT 'A not found';
END IF;
END;//
DELIMITER ;
CALL myupdate();
DROP PROCEDURE myupdate;

Expand to you’re liking comparing the column definition in INFORMATION_SCHEMA.COLUMNS for A & B if you need finer control.