欧美bbbwbbbw肥妇,免费乱码人妻系列日韩,一级黄片

MySQL的CASE WHEN語句的幾個使用實例

 更新時間：2014年05月13日 10:00:19   作者：  
這篇文章主要介紹了MySQL的CASE WHEN語句的幾個使用實例,需要的朋友可以參考下

使用CASE WHEN進行字符串替換處理

復(fù)制代碼 代碼如下:
mysql> select * from sales;

9 rows in set (0.01 sec)

SELECT name AS Name,
    CASE category
    WHEN "Holiday" THEN "Seasonal"
    WHEN "Profession" THEN "Bi_annual"
    WHEN "Literary" THEN "Random" END AS "Pattern"
FROM sales;                   

9 rows in set (0.00 sec)

CREATE TABLE sales(
    num MEDIUMINT NOT NULL AUTO_INCREMENT, name CHAR(20), winter INT, spring INT,
    summer INT, fall INT, category CHAR(13), primary key(num)
) ENGINE=MyISAM;

insert into sales value(1, 'Java', 1067 , 200, 150, 267,'Holiday');
insert into sales value(2, 'C',970,770,531,486,'Profession');
insert into sales value(3, 'JavaScript',53,13,21,856,'Literary');
insert into sales value(4, 'SQL',782,357,168,250,'Profession');
insert into sales value(5, 'Oracle',589,795,367,284,'Holiday');
insert into sales value(6, 'MySQL',953,582,336,489,'Literary');
insert into sales value(7, 'Cplus',752,657,259,478,'Literary');
insert into sales value(8, 'Python',67,23,83,543,'Holiday');
insert into sales value(9, 'PHP',673,48,625,52,'Profession');


簡單語句
復(fù)制代碼 代碼如下:

SELECT CASE WHEN 10*2=30 THEN '30 correct'
   WHEN 10*2=40 THEN '40 correct'
   ELSE 'Should be 10*2=20'
END AS `result`;

多重表達式
復(fù)制代碼 代碼如下:
SELECT CASE 10*2
   WHEN 20 THEN '20 correct'
   WHEN 30 THEN '30 correct'
   WHEN 40 THEN '40 correct'
   ELSE 'No results'
END AS `result`;

在SELECT查詢中使用CASE WHEN
復(fù)制代碼 代碼如下:
CREATE TABLE DVDs (
   ID SMALLINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
   Name VARCHAR(60) NOT NULL,
   NumDisks TINYINT NOT NULL DEFAULT 1,
   RatingID VARCHAR(4) NOT NULL,
   StatID CHAR(3) NOT NULL
) ENGINE=INNODB;
INSERT INTO DVDs (Name, NumDisks, RatingID, StatID)
VALUES ('Christmas', 1, 'NR', 's1'), ('Doc', 1, 'G',  's2'), ('Africa', 1, 'PG', 's1'), ('Falcon', 1, 'NR', 's2'),
       ('Amadeus', 1, 'PG', 's2'), ('Show', 2, 'NR', 's2'), ('View', 1, 'NR', 's1'), ('Mash', 2, 'R',  's2');
SELECT Name, RatingID AS Rating,
   CASE RatingID
      WHEN 'R' THEN 'Under 17 requires an adult.'
      WHEN 'X' THEN 'No one 17 and under.'
      WHEN 'NR' THEN 'Use discretion when renting.'
      ELSE 'OK to rent to minors.'
   END AS Policy
FROM DVDs
ORDER BY Name;

8 rows in set (0.01 sec)

相關(guān)文章

最新評論