mysql - 如何在 sql 查询中替换 UNION

Question

我有一张表:attb

------------------------------------------------
Id | Name | Code | Attribute | Amount 
------------------------------------------------
1  | AV   | 123  | Alpha     | 233
------------------------------------------------
2  | TV   | 122  | Beta      | 235
------------------------------------------------
3  | TV   | 123  | Gama      | 238
------------------------------------------------
4  | CD   | 122  | Beta      | 239
------------------------------------------------
5  | TP   | 122  | Beta      | 240
------------------------------------------------
6  | RX   | 123  | Alpha     | 241
------------------------------------------------

我正在查询它:

select id,name, code, attribute, amount
from attb
where code = 123 and attribute='Alpha'
UNION
select id,name, code, attribute, amount
from attb
where code = 122;

它返回以下内容

---

Id | Name | Code | Attribute | Amount 
------------------------------------------------
1  | AV   | 123  | Alpha     | 233
------------------------------------------------
2  | TV   | 122  | Beta      | 235
------------------------------------------------
4  | CD   | 122  | Beta      | 239
------------------------------------------------
5  | TP   | 122  | Beta      | 240
------------------------------------------------
6  | RX   | 123  | Alpha     | 241
------------------------------------------------

有没有一种方法可以合并两个查询而不是使用 UNION 运算符？或任何更好的实现？

Answer 1

只需将两个 where 子句放在一个查询中:

select id,name, code, attribute, amount
from attb
where (code = 123 and attribute='Alpha') 
   or code = 122;

输出:

id  name  code  attribute  amount
1   AV    123   Alpha      233 
2   TV    122   Beta       235 
4   CD    122   Beta       239 
5   TP    122   Beta       240 
6   RX    123   Alpha      241 

SQLFiddle demo