DB2/400中的if-else语句

Question

我试图在AS400中运行包含if-else语句的SQL,但它不起作用.我正在使用i Series Navigator创建一个View以运行它.

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 . . 

我尝试没有写作是null但相反

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

然后我收到以下错误:

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

Answer 1

CASE改为使用表达式:

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