如何在选择查询中添加if-then-else条件？

Question

我想在a中应用以下条件select query.

IF  (TYPE = MBUSA or SDSA or MDSA OR PC) and (FINAL_STATUS = ACTIVE OR EXECUTED) 
then GET ID and Parent_ID
ELSEIF (TYPE = MSA) and (FINAL_STATUS = ACTIVE OR EXECUTED)
then  GET ID---(USING the ID from the else if condition AS FILTER, 
IF TYPE = (DSA OR BUSA) AND (FINAL_STATUS = ACTIVE OR EXECUTED) 
then GET ID and Parent_ID)

我需要写一个程序吗？

以下是数据库结构:

Answer 1

该CASE语句可用作语句的等效IF.. THEN... ELSE...语句.不太确定你是如何选择它们的,因为你的问题不清楚,所以这里有一些建议.

要使用条件格式的字符串表示形式选择单个列:

SELECT
    CASE
        WHEN (TYPE IN ('MBUSA','SDSA','MDSA','PC') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN ID + ' ' + P_ID
        WHEN ((TYPE = 'MSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED'))
            THEN ID
        WHEN (TYPE IN ('DSA','BUSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN ID + ' ' + P_ID
        ELSE ''
    END AS columnName
FROM
    tableName

要将每个选择到单独的列中

SELECT
    CASE
        WHEN (TYPE IN ('MBUSA','SDSA','MDSA','PC') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN ID
        WHEN ((TYPE = 'MSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED'))
            THEN ID
        WHEN (TYPE IN ('DSA','BUSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN ID
        ELSE ''
    END AS columnOneName
    CASE
        WHEN (TYPE IN ('MBUSA','SDSA','MDSA','PC') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN P_ID
        WHEN ((TYPE = 'MSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED'))
            THEN NULL
        WHEN (TYPE IN ('DSA','BUSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
            THEN  P_ID
        ELSE ''
    END AS columnTwoName
FROM
    tableName

虽然看上面的内容(我可能错误地转录了你的逻辑)但是当你可以逃避2时,有三个案例陈述:

CASE
    WHEN (TYPE IN ('MBUSA','SDSA','MDSA','PC','DSA','BUSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED')) 
        THEN ID + ' ' + P_ID
    WHEN ((TYPE = 'MSA') AND (FINAL_STATUS IN ('ACTIVE','EXECUTED'))
        THEN ID
    ELSE ''
END AS columnName

我知道你现在已经放了一个屏幕截图,但是一个SQL小提琴可能会更有帮助或更详细,以便表名等可以很容易

有用的链接:

http://technet.microsoft.com/en-us/library/ms181765.aspx

SQL案例语句语法？

http://blog.sqlauthority.com/2007/04/14/sql-server-case-statementexpression-examples-and-explanation/