1
CREATE TABLE t1 (a INT, b CHAR(10), INDEX b_key USING BTREE (b(5) DESC)) ENGINE=MyISAM;
2
CREATE TABLE t2 (a INT, b CHAR(10), INDEX b_key USING BTREE (b(2) DESC)) ENGINE=Innodb;
3
CREATE TABLE t3 (a INT, b CHAR(10), INDEX b_key USING HASH (b)) ENGINE=MEMORY;