Question

I am setting up a table in mysql of engine type merge in mysql and was wondering if i have to have all my tables created previously that i want to merge. For example:

CREATE TABLE t1 (
   a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   message CHAR(20)) ENGINE=MyISAM;

CREATE TABLE t2 (
   a INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   message CHAR(20)) ENGINE=MyISAM;
INSERT INTO t1 (message) VALUES ('Testing'),('table'),('t1');
INSERT INTO t2 (message) VALUES ('Testing'),('table'),('t2');
CREATE TABLE total (
   a INT NOT NULL AUTO_INCREMENT,
   message CHAR(20), INDEX(a))
   ENGINE=MERGE UNION=(t1,t2) INSERT_METHOD=LAST;

Now if i have code that automatically created a t3 table i would have to modify the merge table to add this to the union? Would i use an ALTER query for that?

note: i am not using MySQL partitions because i have a mysql version 5.0.

Answer 1

Now if i have code that automatically created a t3 table i would have to modify the merge table to add this to the union? Would i use an ALTER query for that?

From the documentation:

To remap a MERGE table to a different collection of MyISAM tables, you can use one of the following methods:

• DROP the MERGE table and re-create it.
• Use ALTER TABLE tbl_name UNION=(...) to change the list of underlying tables.

Beginning with MySQL 5.0.60, it is also possible to use ALTER TABLE ... UNION=() (that is, with an empty UNION clause) to remove all of the underlying tables.