为什么mysql在使用视图时不使用相同的索引，就像运行查询whitout视图时一样：
在我发表观点之前的查询：
DESCRIBE SELECT membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death, COALESCE(memberships.death, '2099-12-31 23:59:59') AS to_date
FROM memberships
LEFT JOIN groups ON (group_id = target_id)
LEFT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11
AND member_id = 5613956;
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| 1 | SIMPLE | memberships | ref | member,target | member | 10 | const,const | 6 | Using where; Using index |
| 1 | SIMPLE | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
| 1 | SIMPLE | citizens | const | citizen_id | citizen_id | 8 | const | 1 | |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
它工作正常，并且很快，每次我想调试成员资格时，它只需要很长时间。 所以我根据该查询创建了一个视图：
CREATE VIEW group_members AS
SELECT membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death, COALESCE(memberships.death, '2099-12-31 23:59:59') AS to_date
FROM memberships
LEFT JOIN groups ON (group_id = target_id)
LEFT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11;
但是当我尝试获取5613956的会员资格时，我得到了这个：
DESCRIBE SELECT * FROM group_members WHERE citizen_id = 5613956;
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
| 1 | SIMPLE | memberships | ref | member,target | target | 1 | const | 5269 | Using where; Using index |
| 1 | SIMPLE | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
| 1 | SIMPLE | citizens | ALL | NULL | NULL | NULL | NULL | 4766712 | Using where |
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
为什么公民的“possible_keys”为空？
字段citizen_id是SERIAL (= BIGINT(20) UNSIGNED UNIQUE NOT NULL AUTO_INCREMENT)
编辑1
如果我在第一个查询中使用citizen_id insted of member_id，我得到：
DESCRIBE SELECT membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death, COALESCE(memberships.death, '2099-12-31 23:59:59') AS to_date
FROM memberships
LEFT JOIN groups ON (group_id = target_id)
LEFT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11
AND citizen_id = 5613956;
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| 1 | SIMPLE | citizens | const | citizen_id | citizen_id | 8 | const | 1 | |
| 1 | SIMPLE | memberships | ref | member,target | member | 10 | const,const | 6 | Using where; Using index |
| 1 | SIMPLE | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
编辑2
RIGHT JOIN将问题移到insted的成员表中。 （1054 x需要行，与先前的4 766 712 x所需行相比）
CREATE VIEW group_members AS
SELECT membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death, COALESCE(memberships.death, '2099-12-31 23:59:59') AS to_date
FROM memberships
RIGHT JOIN groups ON (group_id = target_id)
RIGHT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11;
DESCRIBE SELECT * FROM group_members WHERE citizen_id = 5613956;
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+-------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+-------+--------------------------+
| 1 | SIMPLE | citizens | const | citizen_id | citizen_id | 8 | const | 1 | |
| 1 | SIMPLE | memberships | index | NULL | member | 45 | NULL | 10540 | Using where; Using index |
| 1 | SIMPLE | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+-------+--------------------------+
编辑3 一个有趣的说明：这更快，因为它使用索引，视图本身失败
SELECT * FROM (SELECT * FROM group_members) AS t WHERE citizen_id = 5613956;
6 rows in set (0.03 sec)
DESCRIBE SELECT * FROM (SELECT * FROM group_members) AS t WHERE citizen_id = 5613956;
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 4423 | Using where |
| 2 | DERIVED | memberships | ref | member,target | target | 1 | | 5270 | Using where; Using index |
| 2 | DERIVED | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
| 2 | DERIVED | citizens | eq_ref | citizen_id | citizen_id | 8 | interfaceways.memberships.member_id | 1 | |
+----+-------------+-------------+--------+---------------+------------+---------+-------------------------------------+------+--------------------------+
编辑4 YaKs评论
CREATE VIEW group_members AS
SELECT membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death
FROM memberships
LEFT JOIN groups ON (group_id = target_id)
LEFT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11;
DESCRIBE SELECT * FROM group_members WHERE citizen_id = 5613956;
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
| 1 | SIMPLE | memberships | ref | member,target | target | 1 | const | 5270 | Using where; Using index |
| 1 | SIMPLE | groups | eq_ref | group_id | group_id | 8 | interfaceways.memberships.target_id | 1 | |
| 1 | SIMPLE | citizens | ALL | NULL | NULL | NULL | NULL | 4766736 | Using where |
+----+-------------+-------------+--------+---------------+----------+---------+-------------------------------------+---------+--------------------------+
编辑5 jcho360评论
ANALYZE TABLE group_members;
+-----------------------------+---------+----------+-------------------------------------------------+
| Table | Op | Msg_type | Msg_text |
+-----------------------------+---------+----------+-------------------------------------------------+
| interfaceways.group_members | analyze | Error | 'interfaceways.group_members' is not BASE TABLE |
| interfaceways.group_members | analyze | error | Corrupt |
+-----------------------------+---------+----------+-------------------------------------------------+
2 rows in set (0.00 sec)
ANALYZE TABLE memberships;
+---------------------------+---------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+---------------------------+---------+----------+----------+
| interfaceways.memberships | analyze | status | OK |
+---------------------------+---------+----------+----------+
1 row in set (0.02 sec)
ANALYZE TABLE citizens;
+------------------------+---------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+------------------------+---------+----------+----------+
| interfaceways.citizens | analyze | status | OK |
+------------------------+---------+----------+----------+
1 row in set (0.11 sec)
ANALYZE TABLE groups;
+----------------------+---------+----------+----------+
| Table | Op | Msg_type | Msg_text |
+----------------------+---------+----------+----------+
| interfaceways.groups | analyze | status | OK |
+----------------------+---------+----------+----------+
1 row in set (0.01 sec)
答案 0 :(得分：0)
我打算添加评论但是太多了。
试试这个：
Select * from
(SELECT member_id, membership_id, group_id, groups.name AS group_name, citizen_id, citizens.name, citizens.family, citizens.identification, memberships.birth, memberships.death, COALESCE(memberships.death, '2099-12-31 23:59:59') AS to_date
FROM memberships
LEFT JOIN groups ON (group_id = target_id)
LEFT JOIN citizens ON (citizen_id = member_id)
WHERE target_type = 31 AND member_type = 11) as table1
where member_id = 5613956;
如果您愿意，可以对该查询进行描述。我认为视图表也是如此，因此where member_id=5613956不会使用公民id索引，因为它没有在where条件中用于显示该查询。所以查询不完全相同。