Question

我有这个表，我希望有一个select语句，根据给定的代码选择VALUE。可能需要CASE语句，但到目前为止我查看的所有示例都有不同的值作为案例的结果。

表A

ID      ||    VALUE 
1       ||    value1 
2       ||    value2 
3       ||    value3 
4       ||    value4 
5       ||    value5 
6       ||    value3 
7       ||    value2 
8       ||    value8

表B

ID         ||CODE 
1          ||1    
2          ||2    
3          ||3    
4          ||4    
5          ||1    
6          ||2    
7          ||3    
8          ||4    


SELECT B.CODE,
         CASE 
          WHEN B.CODE = '01' THEN A.value based on code 
          WHEN B.CODE = '02' THEN A.value based on code 
          WHEN B.CODE = '03' THEN A.value based on code 
          WHEN B.CODE = '04' THEN A.value based on code  
          END AS VALUE_OUT
          FROM  A  JOIN  B
                ON A.ID = B.ID;

Answer 1

您可能只需要一个static子句

WHERE

修改

看起来Select Value From MyTable Where Code = 1就足够了：

INNER JOIN

Answer 2

我想你只想

SELECT DISTINCT
code, value
FROM MyTable

或

SELECT DISTINCT
value
FROM MyTable
WHERE code = 1

如果您想要特定代码的所有值。

SELECT语句中的CASE

2 个答案: