SELECT SQL_NO_CACHE
`Table1`.`recordID`
FROM
`Table1`
LEFT JOIN `Table3` ON `Table3`.`table1RecordID`=`Table1`.`recordID`
WHERE
(`Table3`.`status` = '3' OR `Table3`.`status` = '4') AND
(`Table1`.`groupName` = 'Sample Name')
GROUP BY `Table3`.`recordID` ASC, `Table1`.`recordID` ASC;
+----+-------------+--------+--------+------------------------------+---------+---------+------------------------------+-------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+--------+--------+------------------------------+---------+---------+------------------------------+-------+----------------------------------------------+ | 1 | SIMPLE | Table3 | ALL | fk_packageID,regStatus,pkgID | NULL | NULL | NULL | 11322 | Using where; Using temporary; Using filesort | | 1 | SIMPLE | Table1 | eq_ref | PRIMARY,groupName | PRIMARY | 4 | testDb.Table3.table1RecordID | 1 | Using where | +----+-------------+--------+--------+------------------------------+---------+---------+------------------------------+-------+----------------------------------------------+
如果我删除GROUP BY的第二部分，“Table1。recordID ASC”但是当我这样做时数据不正确。为什么要这样做以及如何修复它，除了Table3之外还要按Table1分组。
先谢谢！
我有时间进行完整查询并将表拉到通用表单，以便在没有客户端数据的情况下发布。我能够将架构添加到sqlfiddle，但没有我使用的数据结果可能会有所不同，由于字符的限制，我甚至无法将100行预表（总共7行）放入sqlfiddle。所以相反，我已经完成了表的转储，我通过Dropbox分享它。
https://www.dropbox.com/s/9fgu626996utpar/stackoverflow-21291707_test_db_schema_and_data.sql
SELECT
`t1`.`name` AS `Object1.Name`,
GROUP_CONCAT(DISTINCT
IF(`t5`.`questionID`=68,
IF(`t6`.`writeInRequired` = 1,
CONCAT(
`t6`.`value`,
':', `t5`.`writeInResponse`
),
`t6`.`value`
),
NULL
) SEPARATOR ', ') AS `Object3.Response_68`,
GROUP_CONCAT(DISTINCT
IF(`t5`.`questionID`=67,
IF(`t6`.`writeInRequired` = 1,
CONCAT(
`t6`.`value`,
':', `t5`.`writeInResponse`
),
`t6`.`value`
),
NULL
) SEPARATOR ', ') AS `Object3.Response_67`,
GROUP_CONCAT(DISTINCT
IF(`t5`.`questionID`=66,
IF(`t6`.`writeInRequired` = 1,
CONCAT(
`t6`.`value`,
':', `t5`.`writeInResponse`
),
`t6`.`value`
),
NULL
) SEPARATOR ', ') AS `Object3.Response_66`,
`t7`.`firstName` AS `Object8.FirstName`,
`t7`.`lastName` AS `Object8.LastName`,
`t7`.`email` AS `Object8.Email`,
`t1`.`recordID` AS `Object1.PackageID`,
`t3`.`recordID` AS `Object5.RegistrationID`
FROM
`Table1` t1
LEFT JOIN `Table2` t2 ON `t1`.`recordID`=`t2`.`table1RecordID`
LEFT JOIN `Table3` t3 ON `t3`.`table1RecordID`=`t1`.`recordID`
LEFT JOIN `Table4` t4 ON `t4`.`table3RecordID`=`t3`.`recordID` AND `t4`.`type` = 1
LEFT JOIN `Table5` t5 ON `t5`.`objectID`=`t3`.`recordID` AND `t5`.`objectType`='Type2'
LEFT JOIN `Table6` t6 ON `t6`.`recordID`=`t5`.`table6RecordID`
JOIN `Table7` t7 ON `t7`.`recordID`=`t4`.`table7RecordID`
WHERE
`t3`.`status` IN ('3','4')
GROUP BY
`Object5.RegistrationID` ASC,
`Object1.PackageID` ASC
*************************** 1. row ***************************
id: 1
select_type: SIMPLE
table: t7
type: ALL
possible_keys: PRIMARY
key: NULL
key_len: NULL
ref: NULL
rows: 11627
filtered: 100.00
Extra: Using temporary; Using filesort
*************************** 2. row ***************************
id: 1
select_type: SIMPLE
table: t4
type: ref
possible_keys: idx_table7RecordID,idx_table3RecordID
key: idx_table7RecordID
key_len: 5
ref: testDb.t7.recordID
rows: 1
filtered: 100.00
Extra: Using where
*************************** 3. row ***************************
id: 1
select_type: SIMPLE
table: t3
type: eq_ref
possible_keys: PRIMARY,table1RecordID_status,idx_status,idx_table1RecordID
key: PRIMARY
key_len: 4
ref: testDb.t4.table3RecordID
rows: 1
filtered: 100.00
Extra: Using where
*************************** 4. row ***************************
id: 1
select_type: SIMPLE
table: t5
type: ref
possible_keys: compositeIDs
key: compositeIDs
key_len: 773
ref: const,testDb.t3.recordID
rows: 5
filtered: 100.00
Extra:
*************************** 5. row ***************************
id: 1
select_type: SIMPLE
table: t6
type: eq_ref
possible_keys: PRIMARY
key: PRIMARY
key_len: 4
ref: testDb.t5.table6RecordID
rows: 1
filtered: 100.00
Extra:
*************************** 6. row ***************************
id: 1
select_type: SIMPLE
table: t1
type: eq_ref
possible_keys: PRIMARY
key: PRIMARY
key_len: 4
ref: testDb.t3.table1RecordID
rows: 1
filtered: 100.00
Extra:
*************************** 7. row ***************************
id: 1
select_type: SIMPLE
table: t2
type: ref
possible_keys: idx_table1RecordID
key: idx_table1RecordID
key_len: 5
ref: testDb.t1.recordID
rows: 85
filtered: 100.00
Extra: Using index
7 rows in set, 1 warning (0.13 sec)
+----+-------------+-------+--------+-------------------------------------------------------------+--------------------+---------+--------------------------+-------+----------+---------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | filtered | Extra | +----+-------------+-------+--------+-------------------------------------------------------------+--------------------+---------+--------------------------+-------+----------+---------------------------------+ | 1 | SIMPLE | t7 | ALL | PRIMARY | NULL | NULL | NULL | 11627 | 100.00 | Using temporary; Using filesort | | 1 | SIMPLE | t4 | ref | idx_table7RecordID,idx_table3RecordID | idx_table7RecordID | 5 | testDb.t7.recordID | 1 | 100.00 | Using where | | 1 | SIMPLE | t3 | eq_ref | PRIMARY,table1RecordID_status,idx_status,idx_table1RecordID | PRIMARY | 4 | testDb.t4.table3RecordID | 1 | 100.00 | Using where | | 1 | SIMPLE | t5 | ref | compositeIDs | compositeIDs | 773 | const,testDb.t3.recordID | 5 | 100.00 | | | 1 | SIMPLE | t6 | eq_ref | PRIMARY | PRIMARY | 4 | testDb.t5.table6RecordID | 1 | 100.00 | | | 1 | SIMPLE | t1 | eq_ref | PRIMARY | PRIMARY | 4 | testDb.t3.table1RecordID | 1 | 100.00 | | | 1 | SIMPLE | t2 | ref | idx_table1RecordID | idx_table1RecordID | 5 | testDb.t1.recordID | 85 | 100.00 | Using index | +----+-------------+-------+--------+-------------------------------------------------------------+--------------------+---------+--------------------------+-------+----------+---------------------------------+
再次感谢先进！
删除了select子句，只需选择第一个表的recordID即可。此查询仍然会从上面生成相同的解释。
SELECT
`t1`.`recordID`
FROM
`Table1` t1
LEFT JOIN `Table2` t2 ON `t1`.`recordID`=`t2`.`table1RecordID`
LEFT JOIN `Table3` t3 ON `t3`.`table1RecordID`=`t1`.`recordID`
LEFT JOIN `Table4` t4 ON `t4`.`table3RecordID`=`t3`.`recordID` AND `t4`.`type` = 1
LEFT JOIN `Table5` t5 ON `t5`.`objectID`=`t3`.`recordID` AND `t5`.`objectType`='Type2'
LEFT JOIN `Table6` t6 ON `t6`.`recordID`=`t5`.`table6RecordID`
JOIN `Table7` t7 ON `t7`.`recordID`=`t4`.`table7RecordID`
WHERE
`t3`.`status` IN ('3','4')
GROUP BY
`t3`.`recordID` ASC,
`t1`.`recordID` ASC;
答案 0 :(得分：0)
有关您的查询的一些评论：
where子句撤消外部联接。Table1进行分组。recordID就足够了。in比or的一系列比较更具可读性。以下是生成的查询：
SELECT SQL_NO_CACHE t1.`recordID`
FROM `Table1` t1 JOIN
`Table3` t3
ON t3.`table1RecordID` = t1.`recordID`
WHERE t3.`status` in ('3', '4') AND
t1.`groupName` = 'Sample Name'
GROUP BY t1.`recordID` ASC;
这表现更好吗？
如果没有，请考虑查询正在做什么。它正在尝试根据t1中的内容过滤掉t3中的记录。假设table1.RecordId是唯一的，那么这将起作用：
SELECT SQL_NO_CACHE t1.`recordID`
FROM `Table1` t1
WHERE t1.`groupName` = 'Sample Name' and
exists (select 1
from Table3 t3
where t3.`status` in ('3', '4') and
t1.RecordId = t3.RecordId
);
为获得最佳效果，您应该在Table3(RecordId, status)上设置索引。