我有一些SQL代码正是我想要的：
select 10 as number, "Checklist 10 Foo" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
from checklist_10
union all
select 11 as number, "Checklist 11 Bar" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
from checklist_11
union all
select 12 as number, "Checklist 12 Baz" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
from checklist_12
group by callsign, number
order by max_ts
结果：
number,name,max(id),max_ts,callsign,max(time_hint_utc),count(*)
10,Checklist 10 Foo,2,1486554484635,VRTEST,2017-02-08 12:21:32,2
11,Checklist 11 Bar,2,1486554490674,VRTEST,2017-02-08 12:21:39,2
12,Checklist 12 Baz,2,1486554496378,VRTEST,2017-02-08 12:21:44,2
12,Checklist 12 Baz,3,1486554496379,VRTEST2,2017-02-08 12:21:45,1
特别是，我看到max()和count()的正确结果，即每个max / count的{{1}}和callsign组合，而不是个人number。
这怎么办？聚合函数看起来像，就像它们在表级selects中一样，但它们的功能就像它们是selects'ed结果的函数一样。
P.S。很抱歉提出一个问题，唯一的问题是我缺乏理解。
使用表格描述进行更新：
union all数据：
mysql> describe checklist_10;
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
| ts | bigint(20) unsigned | NO | | NULL | |
| callsign | varchar(20) | NO | | NULL | |
| smg_id | tinyint(3) unsigned | NO | | NULL | |
| time | int(11) | NO | | NULL | |
| time_hint_utc | datetime | NO | | NULL | |
| reason | enum('UNKNOWN','PERIODIC','SHIFT','MENU','EVENT','DECLINED') | NO | | NULL | |
| foo0 | tinyint(1) | NO | | NULL | |
| foo1 | tinyint(1) | NO | | NULL | |
| foo2 | tinyint(1) | NO | | NULL | |
| foo3 | tinyint(1) | NO | | NULL | |
| foo4 | tinyint(1) | NO | | NULL | |
| foo5 | tinyint(1) | NO | | NULL | |
| foo6 | tinyint(1) | NO | | NULL | |
| foo7 | tinyint(1) | NO | | NULL | |
| foo8 | tinyint(1) | NO | | NULL | |
| foo9 | tinyint(1) | NO | | NULL | |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
17 rows in set (0.00 sec)
mysql> describe checklist_11;
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
| ts | bigint(20) unsigned | NO | | NULL | |
| callsign | varchar(20) | NO | | NULL | |
| smg_id | tinyint(3) unsigned | NO | | NULL | |
| time | int(11) | NO | | NULL | |
| time_hint_utc | datetime | NO | | NULL | |
| reason | enum('UNKNOWN','PERIODIC','SHIFT','MENU','EVENT','DECLINED') | NO | | NULL | |
| bar0 | tinyint(1) | NO | | NULL | |
| bar1 | tinyint(1) | NO | | NULL | |
| bar2 | tinyint(1) | NO | | NULL | |
| bar3 | tinyint(1) | NO | | NULL | |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
11 rows in set (0.00 sec)
mysql> describe checklist_12;
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
| id | bigint(20) unsigned | NO | PRI | NULL | auto_increment |
| ts | bigint(20) unsigned | NO | | NULL | |
| callsign | varchar(20) | NO | | NULL | |
| smg_id | tinyint(3) unsigned | NO | | NULL | |
| time | int(11) | NO | | NULL | |
| time_hint_utc | datetime | NO | | NULL | |
| reason | enum('UNKNOWN','PERIODIC','SHIFT','MENU','EVENT','DECLINED') | NO | | NULL | |
| baz0 | tinyint(1) | NO | | NULL | |
| baz1 | tinyint(1) | NO | | NULL | |
| baz2 | tinyint(1) | NO | | NULL | |
| baz3 | tinyint(1) | NO | | NULL | |
| baz4 | tinyint(1) | NO | | NULL | |
+---------------+--------------------------------------------------------------+------+-----+---------+----------------+
12 rows in set (0.00 sec)
没有1054错误：
mysql> select * from checklist_10;
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+------+------+------+------+------+
| id | ts | callsign | smg_id | time | time_hint_utc | reason | foo0 | foo1 | foo2 | foo3 | foo4 | foo5 | foo6 | foo7 | foo8 | foo9 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+------+------+------+------+------+
| 1 | 1486554385343 | VRTEST | 7 | 1486556393 | 2017-02-08 12:19:53 | PERIODIC | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 0 | 0 |
| 2 | 1486554484635 | VRTEST | 7 | 1486556492 | 2017-02-08 12:21:32 | SHIFT | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+------+------+------+------+------+
2 rows in set (0.00 sec)
mysql> select * from checklist_11;
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+
| id | ts | callsign | smg_id | time | time_hint_utc | reason | bar0 | bar1 | bar2 | bar3 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+
| 1 | 1486554457077 | VRTEST | 7 | 1486556465 | 2017-02-08 12:21:05 | PERIODIC | 0 | 0 | 0 | 0 |
| 2 | 1486554490674 | VRTEST | 7 | 1486556499 | 2017-02-08 12:21:39 | SHIFT | 1 | 1 | 1 | 1 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+
2 rows in set (0.00 sec)
mysql> select * from checklist_12;
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+
| id | ts | callsign | smg_id | time | time_hint_utc | reason | baz0 | baz1 | baz2 | baz3 | baz4 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+
| 1 | 1486554476903 | VRTEST | 7 | 1486556485 | 2017-02-08 12:21:25 | PERIODIC | 1 | 1 | 1 | 1 | 1 |
| 2 | 1486554496378 | VRTEST | 7 | 1486556504 | 2017-02-08 12:21:44 | SHIFT | 1 | 1 | 1 | 1 | 1 |
| 3 | 1486554496379 | VRTEST2 | 7 | 1486556505 | 2017-02-08 12:21:45 | SHIFT | 1 | 1 | 1 | 1 | 1 |
+----+---------------+----------+--------+------------+---------------------+----------+------+------+------+------+------+
3 rows in set (0.00 sec)
答案 0 :(得分：2)
它不像您认为的那样有效。根据{{3}}，
如果在不包含GROUP BY子句的语句中使用组函数，则它等同于对所有行进行分组。
所以这里发生的是你有两个隐式group by（总是只返回一行，无论你的数据中是否有不同的呼号）和一个显式group by实际只有分组你的最后一次选择。
因此，对于MySQL，您的查询看起来像
(select 10 as number, "Checklist 10 Foo" as name, max(id), max(ts) as max_ts,
callsign, max(time_hint_utc), count(*)
from checklist_10)
union all
(select 11 as number, "Checklist 11 Bar" as name, max(id), max(ts) as max_ts,
callsign, max(time_hint_utc), count(*)
from checklist_11)
union all
(select 12 as number, "Checklist 12 Baz" as name, max(id), max(ts) as max_ts,
callsign, max(time_hint_utc), count(*)
from checklist_12
group by callsign, number)
order by max_ts
你可以测试这个，例如更改callsign或checklist_10中某一行的checklist_11。它不会按预期分组。或者你可以，例如在第一个或最后一个查询中将别名number重命名为number1。它将（仅）在第一种情况下工作，在后一种情况下，group by现在找不到列number。
此外，在您的情况下，这仅在您禁用documentation sql模式时才有效，因为您的选择列表包含聚合函数以外的列。
答案 1 :(得分：0)
似乎group by与个人selects绑定，但order by对所选内容的union all进行操作。
解决方案是在每个选择中添加group by子句：
mysql> select 10 as number, "Checklist 10 Foo" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
-> from checklist_10
-> group by callsign
->
-> union all
->
-> select 11 as number, "Checklist 11 Bar" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
-> from checklist_11
-> group by callsign
->
-> union all
->
-> select 12 as number, "Checklist 12 Baz" as name, max(id), max(ts) as max_ts, callsign, max(time_hint_utc), count(*)
-> from checklist_12
-> group by callsign
->
-> order by max_ts
-> ;
+--------+------------------+---------+---------------+----------+---------------------+----------+
| number | name | max(id) | max_ts | callsign | max(time_hint_utc) | count(*) |
+--------+------------------+---------+---------------+----------+---------------------+----------+
| 10 | Checklist 10 Foo | 2 | 1486554484635 | VRTEST | 2017-02-08 12:21:32 | 2 |
| 11 | Checklist 11 Bar | 2 | 1486554490674 | VRTEST | 2017-02-08 12:21:39 | 2 |
| 12 | Checklist 12 Baz | 2 | 1486554496378 | VRTEST | 2017-02-08 12:21:44 | 2 |
| 12 | Checklist 12 Baz | 3 | 1486554496379 | VRTEST2 | 2017-02-08 12:21:45 | 1 |
| 10 | Checklist 10 Foo | 3 | 1486554496380 | VRTEST2 | 2017-02-08 12:21:46 | 1 |
+--------+------------------+---------+---------------+----------+---------------------+----------+
5 rows in set (0.00 sec)