Question

我有下表：

Bank:
name  val   amount
John   1     2000
Peter  1     1999
Peter  2     1854
John   2     1888

我正在尝试编写SQL查询以提供以下结果：

name  amountVal1 amountVal2  
John    2000        1888   
Peter   1999        1854

到目前为止，我有这个：

SELECT name,
CASE WHEN val = 1 THEN amount ELSE 0 END AS amountVal1,
CASE WHEN val = 2 THEN amount ELSE 0 END AS amountVal2
FROM bank

然而，它给出了稍微错误的结果：

name  amountVal1 amountVal2  
John    2000        0
Peter   1999        0
John    0          1888   
Peter   0          1854

如何修改查询以提供正确的演示？感谢

Answer 1

SELECT 
  name,
  SUM(CASE WHEN val = 1 THEN amount ELSE 0 END) AS amountVal1,
  SUM(CASE WHEN val = 2 THEN amount ELSE 0 END) AS amountVal2
FROM bank GROUP BY name

Answer 2

看起来您需要自己加入表格。试试这个：

select bank1.name, bank1.amount, bank2.amount
from bank bank1
inner join bank bank2 on 
    bank1.name = bank2.name 
    and bank1.val = 1 
    and bank2.val = 2

SQL查询使用CASE WHEN来转动列

2 个答案: