SQL Server:CASE WHEN OREN ELSE END =>不支持OR

Question

本OR该在WHEN一个子句CASE语句不支持.我怎样才能做到这一点？

CASE ebv.db_no 
    WHEN 22978 OR 23218 OR 23219 THEN 'WECS 9500' 
    ELSE 'WECS 9520' 
END as wecs_system 

Answer 1

该格式要求您使用以下任一种:

CASE ebv.db_no 
  WHEN 22978 THEN 'WECS 9500' 
  WHEN 23218 THEN 'WECS 9500'  
  WHEN 23219 THEN 'WECS 9500' 
  ELSE 'WECS 9520' 
END as wecs_system 

否则,使用:

CASE  
  WHEN ebv.db_no IN (22978, 23218, 23219) THEN 'WECS 9500' 
  ELSE 'WECS 9520' 
END as wecs_system 

Answer 2

CASE
  WHEN ebv.db_no = 22978 OR 
       ebv.db_no = 23218 OR
       ebv.db_no = 23219
  THEN 'WECS 9500' 
  ELSE 'WECS 9520' 
END as wecs_system 

Answer 3

CASE WHEN ebv.db_no  IN (22978, 23218, 23219) THEN 'WECS 9500' 
  ELSE 'WECS 9520' 
END as wecs_system 

Answer 4

您可以使用WHEN具有的表达式之一,但不能将它们混合使用.

1. 当when_expression时

   是一个简单的表达式,当使用简单的CASE格式时,input_expression与之比较.when_expression是任何有效的表达式.input_expression和每个when_expression的数据类型必须相同或必须是隐式转换.

2. 什么时候是Boolean_expression

   使用搜索的CASE格式时是否计算布尔表达式.Boolean_expression是任何有效的布尔表达式.

你可以编程:

1.

    CASE ProductLine
            WHEN 'R' THEN 'Road'
            WHEN 'M' THEN 'Mountain'
            WHEN 'T' THEN 'Touring'
            WHEN 'S' THEN 'Other sale items'
            ELSE 'Not for sale'

2.

    CASE
            WHEN ListPrice =  0 THEN 'Mfg item - not for resale'
            WHEN ListPrice < 50 THEN 'Under $50'
            WHEN ListPrice >= 50 and ListPrice < 250 THEN 'Under $250'
            WHEN ListPrice >= 250 and ListPrice < 1000 THEN 'Under $1000'
            ELSE 'Over $1000'
          END

但无论如何,您可以预期变量排名将在布尔表达式中进行比较.

请参阅CASE(Transact-SQL)(MSDN).

Answer 5

已经有很多答案了CASE.我将解释何时以及如何使用CASE.

您可以在SQL查询中的任何位置使用CASE表达式.CASE表达式可以在SELECT语句,WHERE子句,Order by子句,HAVING子句,Insert,UPDATE和DELETE语句中使用.

CASE表达式具有以下两种格式:

1. 简单的CASE表达

   CASE expression
   WHEN expression1 THEN Result1
   WHEN expression2 THEN Result2
   ELSE ResultN
   END
   

   这会将表达式与一组简单表达式进行比较,以查找结果.此表达式将表达式与每个WHEN子句中的表达式进行比较以获得等效性.如果WHEN子句中的表达式匹配,则返回THEN子句中的表达式.

   这是OP的问题正在下降的地方.22978 OR 23218 OR 23219不会得到一个等于表达式的值,即ebv.db_no.这就是为什么它会出错.input_expression和每个when_expression的数据类型必须相同或必须是隐式转换.

2. 搜索CASE表达式

   CASE
   WHEN Boolean_expression1 THEN Result1
   WHEN Boolean_expression2 THEN Result2
   ELSE ResultN
   END
   

   此表达式计算一组布尔表达式以查找结果.此表达式允许在每个布尔表达式中使用比较运算符和逻辑运算符AND/OR.

1.SELECT语句与CASE表达式

--Simple CASE expression: 
SELECT FirstName, State=(CASE StateCode
 WHEN 'MP' THEN 'Madhya Pradesh' 
 WHEN 'UP' THEN 'Uttar Pradesh' 
 WHEN 'DL' THEN 'Delhi' 
 ELSE NULL 
 END), PayRate
FROM dbo.Customer

-- Searched CASE expression:
SELECT FirstName,State=(CASE 
 WHEN StateCode = 'MP' THEN 'Madhya Pradesh' 
 WHEN StateCode = 'UP' THEN 'Uttar Pradesh' 
 WHEN StateCode = 'DL' THEN 'Delhi' 
 ELSE NULL 
 END), PayRate
FROM dbo.Customer

2.带有CASE表达式的更新语句

-- Simple CASE expression: 
UPDATE Customer 
SET StateCode = CASE StateCode
 WHEN 'MP' THEN 'Madhya Pradesh' 
 WHEN 'UP' THEN 'Uttar Pradesh' 
 WHEN 'DL' THEN 'Delhi' 
 ELSE NULL 
 END 

-- Simple CASE expression: 
UPDATE Customer 
SET StateCode = CASE 
 WHEN StateCode = 'MP' THEN 'Madhya Pradesh' 
 WHEN StateCode = 'UP' THEN 'Uttar Pradesh' 
 WHEN StateCode = 'DL' THEN 'Delhi' 
 ELSE NULL 
 END 

带有CASE表达式的3.ORDER BY子句

-- Simple CASE expression: 
SELECT * FROM dbo.Customer
ORDER BY 
 CASE Gender WHEN 'M' THEN FirstName END Desc,
 CASE Gender WHEN 'F' THEN LastName END ASC

-- Searched CASE expression: 
SELECT * FROM dbo.Customer
ORDER BY 
 CASE WHEN Gender='M' THEN FirstName END Desc,
 CASE WHEN Gender='F' THEN LastName END ASC

4.带有CASE表达式的子句

-- Simple CASE expression: 
SELECT FirstName ,StateCode,Gender, Total=MAX(PayRate)
FROM dbo.Customer
GROUP BY StateCode,Gender,FirstName
HAVING (MAX(CASE Gender WHEN 'M' 
 THEN PayRate 
 ELSE NULL END) > 180.00
 OR MAX(CASE Gender WHEN 'F' 
 THEN PayRate 
 ELSE NULL END) > 170.00)

-- Searched CASE expression: 
SELECT FirstName ,StateCode,Gender, Total=MAX(PayRate)
FROM dbo.Customer
GROUP BY StateCode,Gender,FirstName
HAVING (MAX(CASE WHEN Gender = 'M' 
 THEN PayRate 
 ELSE NULL END) > 180.00
 OR MAX(CASE WHEN Gender = 'F' 
 THEN PayRate 
 ELSE NULL END) > 170.00)

希望这个用例将来有助于某人.

资源

Answer 6

尝试

CASE WHEN ebv.db_no IN (22978,23218,23219) THEN 'WECS 9500' ELSE 'WECS 9520' END

Answer 7

SELECT
  Store_Name,
  CASE Store_Name
    WHEN 'Los Angeles' THEN Sales * 2
    WHEN 'San Diego' THEN Sales * 1.5
    ELSE Sales
    END AS "New Sales",
  Txn_Date
FROM Store_Information;