CREATE TABLE tbl (id int, field1 varchar(255));
CREATE INDEX field1_ix ON tbl(field1);
EXPLAIN
SELECT * FROM tbl
WHERE `field1` LIKE '_aa_a_';
EXPLAIN
SELECT * FROM tbl
WHERE `field1` = '_aa_a_';
CREATE FULLTEXT INDEX field1_ft_ix ON tbl(field1);
EXPLAIN
SELECT * FROM tbl
WHERE `field1` LIKE '_aa_a_';
EXPLAIN
SELECT * FROM tbl
WHERE `field1` = '_aa_a_';