關於where子句的case語句？

Question

我對病例陳述有點新，但下面是我的查詢。

Table1 
col1 col2 col3 col4 Month Freeze 
1 13 25 37 1 0 
3 15 27 39 2 1 
4 16 28 40 2 0 
5 17 29 41 3 1 
6 18 30 42 3 0 
7 19 31 43 4 1 
8 20 32 44 4 0 
9 21 33 45 5 1 
10 22 34 46 5 0 
11 23 35 47 6 0 

'結果我要像'：

Select all records from Month1 to Month 12 where 'Freeze = 1' , 
if any month between 1 to 12 does not have Freeze = 1 then give me records for Freeze= 0 'just for the months which does not have 'Freeze = 1' 

我最好的非工作的嘗試：

select * from tb1 where Month between 2 and 6 and freeze = 1 or Month in ('1' ,'2') and freeze = 0 

Answer 1

以下是使用標準SQL的方法：

Select t1.* 
from table1 t1 
where Freeze = 1 and month between 1 and 12 or 
     (not exists (select 1 from table where Freeze = 1 and month between 1 and 12) and 
     month = 0 
    ); 

使用窗口函數，你也可以：

select t1.* 
from (select t1.*, 
      count(case when freeze = 1 and month between 1 and 2) over() as freeze1cnt 
     from table1 t1 
    ) t1 
where month between 1 and 2 and freeze = 1 or 
     month = 0 and freeze1cnt = 0; 

Answer 2

下面是將outer join一個選項：

select t1.* 
from Table1 t1 
    left join Table1 t2 on 
    t1.month = t2.month and t2.freeze = 1 
where t1.freeze = 1 
    and t1.month between 1 and 12 
    or t2.month is null 

• SQL Fiddle Demo

結果：

COL1 COL2 COL3 COL4 MONTH FREEZE 
1  13  25 37 1  0 
3  15  27 39 2  1 
5  17  29 41 3  1 
7  19  31 43 4  1 
9  21  33 45 5  1 
11 23  35 47 6  0 

注意，根據y的我們的數據，您可能需要使用此方法使用distinct。