flush status;
show status like 'Table_lock%';
Variable_name	Value
Table_locks_immediate	0
Table_locks_waited	0
SET SQL_LOG_BIN=0;
drop table if exists t1;
create table t1(n int) engine=myisam;
insert into t1 values(1);
lock tables t1 read;
unlock tables;
lock tables t1 read;
update t1 set n = 3;
unlock tables;
show status like 'Table_lock%';
Variable_name	Value
Table_locks_immediate	3
Table_locks_waited	1
drop table t1;
select 1;
1
1
show status like 'last_query_cost';
Variable_name	Value
Last_query_cost	0.000000
FLUSH STATUS;
SHOW STATUS LIKE 'max_used_connections';
Variable_name	Value
Max_used_connections	1
SET @save_thread_cache_size=@@thread_cache_size;
SET GLOBAL thread_cache_size=3;
SHOW STATUS LIKE 'max_used_connections';
Variable_name	Value
Max_used_connections	3
FLUSH STATUS;
SHOW STATUS LIKE 'max_used_connections';
Variable_name	Value
Max_used_connections	2
SHOW STATUS LIKE 'max_used_connections';
Variable_name	Value
Max_used_connections	3
SHOW STATUS LIKE 'max_used_connections';
Variable_name	Value
Max_used_connections	4
SET GLOBAL thread_cache_size=@save_thread_cache_size;
CREATE TABLE t1 ( a INT );
INSERT INTO t1 VALUES (1), (2);
SELECT a FROM t1 LIMIT 1;
a
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	2.402418
EXPLAIN SELECT a FROM t1;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	2	
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	2.402418
SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
a
1
2
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	0.000000
EXPLAIN SELECT a FROM t1 UNION SELECT a FROM t1 ORDER BY a;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	PRIMARY	t1	ALL	NULL	NULL	NULL	NULL	2	
2	UNION	t1	ALL	NULL	NULL	NULL	NULL	2	
NULL	UNION RESULT	<union1,2>	ALL	NULL	NULL	NULL	NULL	NULL	Using filesort
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	0.000000
SELECT a IN (SELECT a FROM t1) FROM t1 LIMIT 1;
a IN (SELECT a FROM t1)
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	0.000000
SELECT (SELECT a FROM t1 LIMIT 1) x FROM t1 LIMIT 1;
x
1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	0.000000
SELECT * FROM t1 a, t1 b LIMIT 1;
a	a
1	1
SHOW SESSION STATUS LIKE 'Last_query_cost';
Variable_name	Value
Last_query_cost	4.805836
DROP TABLE t1;
DROP PROCEDURE IF EXISTS p1;
DROP FUNCTION IF EXISTS f1;
CREATE FUNCTION f1() RETURNS INTEGER
BEGIN
DECLARE foo INTEGER;
DECLARE bar INTEGER;
SET foo=1;
SET bar=2;
RETURN foo;
END $$
CREATE PROCEDURE p1()
BEGIN
SELECT 1;
END $$
SELECT f1();
f1()
1
CALL p1();
1
1
SELECT 9;
9
9
DROP PROCEDURE p1;
DROP FUNCTION f1;