導(dǎo)讀:1建站知識(shí)本篇文章是對(duì)oracle case when 語句的用法進(jìn)行了詳細(xì)的分析介紹，需要的朋友參考下企業(yè)網(wǎng)站建設(shè)網(wǎng)站優(yōu)化seo培訓(xùn)。

1. CASE WHEN 表達(dá)式有兩種形式

復(fù)制代碼 代碼如下:

--簡單Case函數(shù)  CASE sex  WHEN '1' THEN '男'  WHEN '2' THEN '女'  ELSE '其他' END  --Case搜索函數(shù)  CASEWHEN sex = '1' THEN '男'  WHEN sex = '2' THEN '女'  ELSE '其他' END 

2. CASE WHEN 在語句中不同位置的用法2.1 SELECT CASE WHEN 用法

復(fù)制代碼 代碼如下:

SELECT   grade, COUNT (CASE WHEN sex = 1 THEN 1      /*sex 1為男生，2位女生*/                       ELSE NULL                       EN如何seo優(yōu)化推廣網(wǎng)站D) 男生數(shù),                COUNT (CASE WHEN sex = 2 THEN 1                       ELSE NULL                       seo網(wǎng)站關(guān)鍵詞優(yōu)化END) 女生數(shù)  &建設(shè)網(wǎng)站nbsp; FROM students GROUP BY grade;

2.2 WHERE CASE WHEN 用法

復(fù)制代碼 代碼如下:

SELECT T2.*, T1.*   FROM T1, T2  WHERE (CASE WHEN T2.COMPARE_TYPE = 'A' AND                   T1.SOME_TYPE LIKE 'NOTHING%'                THEN 1              WHEN T2.COMPARE_TYPE != 'A' AND                   T1.SOME_TYPE NOT LIKE 'NOTHING%'                THEN 1              ELSE 0           END) = 1

2.3 GROUP BY CASE WHEN 用法

復(fù)制代碼 代碼如下:

SELECT  CASE WHEN salary <= 500 THEN '1'  WHEN salary > 500 AND salary <= 600  THEN '2'  WHEN salary > 600 AND salary <= 800  THEN '3'  WHEN salary > 800 AND salary <= 1000 THEN '4'  ELSE NULL END salary_class, -- 別名命名COUNT(*)  FROM    Table_A  GROUP BY  CASE WHEN salary <= 500 THEN '1'  WHEN salary > 500 AND salary <= 600  THEN '2'  WHEN salary > 600 AND salary <= 800  THEN '3'  WHEN salary > 800 AND salary <= 1000 THEN '4'  ELSE NULL END; 

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