SELECT CASE WHEN profile.nrefillno = 0 THEN 'N' ELSE 'R'END as newref
From profile

SELECT  
(CASE 
     WHEN (Obsolete = 'N' OR InStock = 'Y') THEN 'YES'
                                            ELSE 'NO' 
 END) as Salable
, * 
FROM Product

CASE语句最接近SQL中的IF，并且在所有版本的SQL Server上都受支持。

SELECT CAST(
             CASE
                  WHEN Obsolete = 'N' or InStock = 'Y'
                     THEN 1
                  ELSE 0
             END AS bit) as Saleable, *
FROM Product

如果希望结果为布尔值，则只需使用CAST运算符。如果您对int感到满意，这将起作用：

SELECT CASE
            WHEN Obsolete = 'N' or InStock = 'Y'
               THEN 1
               ELSE 0
       END as Saleable, *
FROM Product

CASE语句可以嵌入到其他CASE语句中，甚至可以包含在聚合中。

SQL Server Denali（SQL Server 2012）添加了IIF语句，该语句也可用于访问（Martin Smith指出）：

SELECT IIF(Obsolete = 'N' or InStock = 'Y', 1, 0) as Saleable, * FROM Product

作为CASE语句的替代解决方案，可以使用表驱动方法：

DECLARE @Product TABLE (ID INT, Obsolete VARCHAR(10), InStock VARCHAR(10))
INSERT INTO @Product VALUES
(1,'N','Y'),
(2,'A','B'),
(3,'N','B'),
(4,'A','Y')

SELECT P.* , ISNULL(Stmt.Saleable,0) Saleable
FROM
    @Product P
    LEFT JOIN
        ( VALUES
            ( 'N', 'Y', 1 )
        ) Stmt (Obsolete, InStock, Saleable)
        ON  P.InStock = Stmt.InStock OR P.Obsolete = Stmt.Obsolete

结果：

ID          Obsolete   InStock    Saleable
----------- ---------- ---------- -----------
1           N          Y          1
2           A          B          0
3           N          B          1
4           A          Y          1

使用SQL CASE与普通的If/Else语句一样。在下面的查询中，如果过时值=“N”或InStock值=“Y”，则输出将为1。否则，输出将为0。然后我们将0或1值放在Salable列下。

SELECT
      CASE
           WHEN obsolete = 'N' OR InStock = 'Y'
          THEN 1
        ELSE 0
      END AS Salable
      , *
FROM PRODUCT

SELECT 1 AS Saleable, *
  FROM @Product
 WHERE ( Obsolete = 'N' OR InStock = 'Y' )
UNION
SELECT 0 AS Saleable, *
  FROM @Product
 WHERE NOT ( Obsolete = 'N' OR InStock = 'Y' )