MySQL innodb count(*) count(1) 效能比較
阿新 • • 發佈：2019-02-01
EXPLAIN SELECT COUNT(*) FROM gg_bm_o_order;
id select_type TABLE TYPE KEY key_len ref ROWS Extra
------ ----------- ------------- ------ -------------------------- ------- ------ ------ -------------
1 SIMPLE gg_bm_o_order INDEX IDX_ORDER_ORDER_START_TIME 8 (NULL) 42 USING INDEX
EXPLAIN EXTENDED SELECT COUNT(*) FROM gg_bm_o_order;
SHOW WARNINGS;
LEVEL CODE Message
------ ------ -----------------------------------------------------------
Note 1003 SELECT COUNT(0) AS `count(*)` FROM `gg_bm_o_order`
SELECT COUNT(*) FROM gg_bm_o_order;
SHOW STATUS LIKE 'Last_query_cost';
Variable_name VALUE
--------------- ----------
Last_query_cost 9.399000
EXPLAIN SELECT COUNT(1) FROM gg_bm_o_order;
id select_type TABLE TYPE KEY key_len ref ROWS Extra
------ ----------- ------------- ------ -------------------------- ------- ------ ------ -------------
1 SIMPLE gg_bm_o_order INDEX IDX_ORDER_ORDER_START_TIME 8 (NULL) 42 USING INDEX
EXPLAIN EXTENDED SELECT COUNT(1) FROM gg_bm_o_order;
SHOW WARNINGS;
LEVEL CODE Message
------ ------ -----------------------------------------------------------
Note 1003 SELECT COUNT(1) AS `COUNT(1)` FROM `gg_bm_o_order`
SELECT COUNT(1) FROM gg_bm_o_order;
SHOW STATUS LIKE 'Last_query_cost';
Variable_name VALUE
--------------- ----------
Last_query_cost 9.399000
id select_type TABLE TYPE KEY key_len ref ROWS Extra
------ ----------- ------------- ------ -------------------------- ------- ------ ------ -------------
1 SIMPLE gg_bm_o_order INDEX IDX_ORDER_ORDER_START_TIME 8 (NULL) 42 USING INDEX
EXPLAIN EXTENDED SELECT COUNT(*) FROM gg_bm_o_order;
SHOW WARNINGS;
LEVEL CODE Message
------ ------ -----------------------------------------------------------
Note 1003 SELECT COUNT(0) AS `count(*)` FROM `gg_bm_o_order`
SELECT COUNT(*) FROM gg_bm_o_order;
SHOW STATUS LIKE 'Last_query_cost';
Variable_name VALUE
--------------- ----------
Last_query_cost 9.399000
EXPLAIN SELECT COUNT(1) FROM gg_bm_o_order;
id select_type TABLE TYPE KEY key_len ref ROWS Extra
------ ----------- ------------- ------ -------------------------- ------- ------ ------ -------------
1 SIMPLE gg_bm_o_order INDEX IDX_ORDER_ORDER_START_TIME 8 (NULL) 42 USING INDEX
EXPLAIN EXTENDED SELECT COUNT(1) FROM gg_bm_o_order;
SHOW WARNINGS;
LEVEL CODE Message
------ ------ -----------------------------------------------------------
Note 1003 SELECT COUNT(1) AS `COUNT(1)` FROM `gg_bm_o_order`
SELECT COUNT(1) FROM gg_bm_o_order;
SHOW STATUS LIKE 'Last_query_cost';
Variable_name VALUE
--------------- ----------
Last_query_cost 9.399000