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--echo # 'Using index' method is used since wild string is suitable for the use with prefix key. EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'a%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'abcd%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like ''; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'abc\%%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '\%abc%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'abc%%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '%%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '____%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '\_\_\_\_%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '\%\%\%\%'; EXPLAIN SELECT b LIKE 'abcd' FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT b LIKE 'abc%' FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'aaa\\'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'aaa\\\\'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'aaa\\\\%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'a_'; --echo # 'Using index' method is not used since wild string is not suitable for the use with prefix key. EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like '%a'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'a%c%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'a%c'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'abcde%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'abcde%'; EXPLAIN SELECT b FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT b LIKE 'abcde' FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT b LIKE '%bc' FROM t1 WHERE b like 'ab%'; EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'aaaa\\'; --echo # 'Using index' method is not used since wild string is not suitable for the use with prefix key. EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'a%' OR b like '%a'; --echo # 'Using index' method is used since wild string is suitable for the use with prefix key. EXPLAIN SELECT COUNT(*) FROM t1 WHERE b like 'ab%'; --echo # 'Using index' method is not used since 'b' field is used in select output. EXPLAIN SELECT b FROM t1 WHERE b like 'ab%'; --echo # Index k2 shouldn't be used. EXPLAIN SELECT COUNT(*) FROM t1 IGNORE INDEX(k2) WHERE b like 'a%';