Oracle DECODE的标准SQL替代 [英] Standard SQL alternative to Oracle DECODE

问题描述

是否存在与Oracle的DECODE函数等效的ANSI SQL?

Is there an ANSI SQL equivalent to Oracle's DECODE function?

Oracle的解码功能是SQL中的IF-THEN-ELSE构造.

Oracle's decode function is the IF-THEN-ELSE construct in SQL.

推荐答案

CASE表达式是ANSI SQL方法，其中有两个变体，简单"和搜索":

A CASE expression is the ANSI SQL method, of which there are 2 varieties, "simple" and "searched":

1)简单的CASE表达式:

1) Simple CASE expression:

CASE col WHEN 1 THEN 'One'
         WHEN 2 THEN 'Two'
         ELSE 'More'
         END

2)搜索了CASE表达式:

2) Searched CASE expression:

CASE WHEN col < 0 THEN 'Negative'
     WHEN col = 0 THEN 'Zero'
     ELSE 'Positive'
     END

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