DB2/400中的if-else语句 [英] If-else statement in DB2/400

问题描述

我正在尝试在AS400中运行包含if-else语句的SQL，但是它不起作用.我正在使用i Series Navigator创建一个View，以便运行它.

I am trying to run an SQL that contains if-else statement in AS400 but it doesn't work. I am creating a View using i Series Navigator in order to run it.

SELECT IF FIELD1 IS NOT NULL THEN 'AAA' ELSE 'BBB' END IF
FROM LIB.TABLE1

我得到的错误是:

SQL State: 42601
Vendor Code: -199
Message: [SQL0199] Keyword IS not expected. Valid tokens: , FROM INTO. Cause . . 

我尝试不写就为空，而是

I tried without writing is null but instead

SELECT IF FIELD1 ='' THEN 'AAA' ELSE 'BBB' END IF
    FROM LIB.TABLE1

然后出现以下错误:

SQL State: 42601
Vendor Code: -104
Message: [SQL0104] Token = was not valid. Valid tokens: , FROM INTO. Cause . . . . . :   A syntax error was detected at token =.  Token = is not a

推荐答案

请改用 CASE 表达式:

SELECT CASE WHEN FIELD1 IS NOT NULL THEN 'AAA' ELSE 'BBB' END 
FROM LIB.TABLE1;

IF 是控制流构造:

IF condition THEN 
   SELECT ...
ELSE 
   SELECT ...
END IF

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