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[英]Mysql join query not excluding rows with same id if one row fails the join condition
[英]MYSQL: Excluding several rows if one joined row matches a condition
我有兩張桌子。 一個是用戶,其中包含字段uid和名稱。 另一個表是users_roles,其中包含字段uid和rid(role id)。
我想要檢索沒有任何一組提供的角色的用戶列表。
例如:
uid | name
----------
1 | BOB
2 | DAVE
3 | JOHN
USERS_ROLES:
uid | rid
---------
1 | 1
1 | 2
1 | 3
2 | 1
3 | 1
我希望能夠只查詢沒有一組rids的用戶。 例如,排除rid 2和3的查詢應該返回DAVE和JOHN,或者排除rids(1,3)的查詢應該返回nobody。
使用反連接模式的查詢有時是最有效的:
SELECT u.uid
, u.name
FROM users u
LEFT
JOIN users_roles r
ON r.uid = u.uid
AND r.rid IN (2,3)
WHERE r.uid IS NULL
反連接模式是LEFT [outer] JOIN user_roles
表以拉回所有匹配的行,AND來從沒有匹配行的users
獲取行。 “技巧”是在WHERE子句中使用謂詞排除所有匹配行,從而消除具有匹配項的用戶的所有行。
使用NOT EXISTS相關子查詢可以獲得等效的結果集:
SELECT u.uid
, u.name
FROM users u
WHERE NOT EXISTS
( SELECT 1
FROM users_roles r
WHERE r.uid = u.uid
AND r.rid IN (2,3)
)
另一種方法是使用NOT IN
,盡管有時效率較低。 性能取決於許多因素。 優化器可以為每個查詢生成不同的執行計划。
在任何情況下,為了獲得最佳性能,您需要一個索引... ON users_roles (uid)
或ON users_roles (uid,rid)
。
我的MySQL 5.1.34服務器上的性能測試表明,反連接查詢的速度幾乎是等效的NOT EXISTS和NOT IN查詢的兩倍。 (1.091秒對2.066秒和2.020秒)
-- setup and populate test tables
CREATE TABLE t_users
( uid INT UNSIGNED NOT NULL PRIMARY KEY
, `name` VARCHAR(50)
) ENGINE=INNODB DEFAULT CHARSET=latin1 ;
CREATE TABLE t_users_roles
( uid INT UNSIGNED NOT NULL
, rid INT UNSIGNED NOT NULL
, PRIMARY KEY (uid,rid)
) ENGINE=INNODB DEFAULT CHARSET=latin1;
ALTER TABLE t_users_roles ADD CONSTRAINT FK_t_users_roles_t_users FOREIGN KEY (uid) REFERENCES t_users (uid);
CREATE INDEX t_users_ix1 ON t_users (uid,`name`);
CREATE INDEX t_users_roles_ix1 ON t_users_roles (rid,uid);
INSERT INTO t_users (uid,`name`)
SELECT d.d*100000+e.d*10000+u.d*1000+h.d*100+t.d*10+o.d+1 AS uid
, CONCAT('NAME',LPAD(d.d*100000+e.d*10000+u.d*1000+h.d*100+t.d*10+o.d+1,8,'-')) AS `name`
FROM (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) o
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) h
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) u
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) e
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) d
;
-- 1000000 row(s) affected.
INSERT INTO t_users_roles (uid,rid)
SELECT d.d*100000+e.d*10000+u.d*1000+h.d*100+t.d*10+o.d+1 AS uid
, r.rid
FROM (SELECT 1 AS rid UNION ALL SELECT 2 UNION ALL SELECT 3) r
CROSS
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) o
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) t
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) h
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) u
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) e
JOIN (SELECT 0 AS d UNION ALL SELECT 1 UNION ALL SELECT 2 UNION ALL SELECT 3 UNION ALL SELECT 4 UNION ALL SELECT 5 UNION ALL SELECT 6 UNION ALL SELECT 7 UNION ALL SELECT 8 UNION ALL SELECT 9) d
WHERE (d.d*100000+e.d*10000+u.d*1000+h.d*100+t.d*10+o.d+1) % 100000 <> 0
;
-- 2999970 row(s) affected
OPTIMIZE TABLE t_users;
OPTIMIZE TABLE t_users_roles;
SHOW STATUS LIKE 'Qcache_hits' ;
-- Variable_name Value
-- ------------- ---------
-- Qcache_hits 1117342
SHOW VARIABLES LIKE 'version' ;
-- Variable_name Value
-- ------------- ------------
-- version 5.1.53-log
-- table size from the file system
$ du -sh DATA/test/t_users*.ibd
72M DATA/test/t_users.ibd
133M DATA/test/t_users_roles.ibd
-- anti-join query
SELECT SQL_NO_CACHE u.uid
, u.name
FROM t_users u
LEFT
JOIN t_users_roles r
ON r.uid = u.uid
AND r.rid IN (2,3)
WHERE r.uid IS NULL ;
-- Exec: 1.095 sec
-- Exec: 1.090 sec
-- Exec: 1.091 sec
-- Exec: 1.087 sec
-- Exec: 1.090 sec
-- avg 5 executions: 1.091 sec
-- not exists query
SELECT SQL_NO_CACHE u.uid
, u.name
FROM t_users u
WHERE NOT EXISTS
( SELECT 1
FROM t_users_roles r
WHERE r.uid = u.uid
AND r.rid IN (2,3)
) ;
-- Exec: 2.071 sec
-- Exec: 2.066 sec
-- Exec: 2.059 sec
-- Exec: 2.065 sec
-- Exec: 2.070 sec
-- avg 5 executions: 2.066 sec
-- not in query
SELECT SQL_NO_CACHE u.uid
, u.name
FROM t_users u
WHERE u.uid NOT IN
( SELECT r.uid
FROM t_users_roles r
WHERE r.uid IS NOT NULL
AND r.rid IN (2,3)
) ;
-- Exec: 2.022 sec
-- Exec: 2.023 sec
-- Exec: 2.014 sec
-- Exec: 2.026 sec
-- Exec: 2.016 sec
-- avg 5 executions: 2.020 sec
SHOW STATUS LIKE 'Qcache_hits' ;
-- Variable_name Value
-- ------------- ---------
-- Qcache_hits 1117342
EXPLAIN output for three statements:
-- ANTI JOIN
id select_type table type possible_keys key key_len ref rows filtered Extra
-- ------------------ ------ -------------- ------------------------- ----------- ------- ----- ------- -------- ------------------------------------
1 SIMPLE u index t_users_ix1 57 1000423 100.00 Using index
1 SIMPLE r ref PRIMARY,t_users_roles_ix1 PRIMARY 4 u.uid 1 100.00 Using where; Using index; Not exists
-- NOT EXISTS
id select_type table type possible_keys key key_len ref rows filtered Extra
-- ------------------ ------ -------------- ------------------------- ----------- ------- ----- ------- -------- --------------------------
1 PRIMARY u index t_users_ix1 57 1000423 100.00 Using where; Using index
2 DEPENDENT SUBQUERY r ref PRIMARY,t_users_roles_ix1 PRIMARY 4 u.uid 1 100.00 Using where; Using index
-- NOT IN
id select_type table type possible_keys key key_len ref rows filtered Extra
-- ------------------ ------ -------------- ------------------------- ----------- ------- ------ ------- -------- --------------------------
1 PRIMARY u index t_users_ix1 57 1000423 100.00 Using where; Using index
2 DEPENDENT SUBQUERY r index_subquery PRIMARY,t_users_roles_ix1 PRIMARY 4 func 1 100.00 Using index; Using where
您正在尋找NOT IN查詢:
SELECT name
FROM users
WHERE uid NOT IN (SELECT uid FROM Users_roles WHERE rid = 2 OR rid = 3)
查詢會給你他們失蹤的名字都完整列表rid
。
SELECT a.*, b.rid
FROM users a CROSS JOIN
(SELECT DISTINCT rid FROM users_roles) b
LEFT JOIN USERS_ROLES c
ON a.uid = c.uid AND
b.rid = c.rid
WHERE c.rid IS NULL
-- AND other conditions
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