SQL根據列中的值通過不同的條件進行篩選

Question

我有一個可以具有X或Y值的分類器列。如果列中有x或y，我的選擇查詢必須按日期進行篩選。

date BETWEEN i.valid_fromX AND i.valid_toX 
date BETWEEN i.valid_fromY AND i.valid_toY 

基本上我需要在SQL下面的等價：

if classifier == X { 
    check if date is between valid_fromX to valid_toX 
} else if classifier == Y { 
    check if date is between valid_fromY to valid_toY 
} 

Answer 1

你可以做到這一點與常規的和/或邏輯。這個例子搜索月份，如果分類等於X，而2月，如果分類等於Y：

where classifier = 'X' and date between '2012-01-01' and '2012-02-01' 
     or 
     classifier = 'Y' and date between '2012-02-01' and '2012-03-01' 

Answer 2

WHERE (classifier = 'X' AND [date] BETWEEN valid_fromX AND valid_toX) 
     OR (classifier = 'Y' AND [date] BETWEEN valid_fromY AND valid_toY) 

Answer 3

A小調變種：

where date between 
      case classifier when 'X' then valid_fromX when 'Y' then valid_fromY end 
      and case classifier when 'X' then valid_toX when 'Y' then valid_toY end