drop table if exists t1; CREATE TABLE t1 (id CHAR(12) not null, PRIMARY KEY (id)); insert into t1 values ('000000000001'),('000000000002'); explain select * from t1 where id=000000000001; table type possible_keys key key_len ref rows Extra t1 index PRIMARY PRIMARY 12 NULL 2 where used; Using index select * from t1 where id=000000000001; id 000000000001 delete from t1 where id=000000000002; select * from t1; id 000000000001 drop table t1;