MySQL 高级函数

15 的 2 进制编码:

SELECT BIN(15); -- 1111

SELECT BINARY "RUNOOB";
-> RUNOOB

CASE expression
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
   ...
    WHEN conditionN THEN resultN
    ELSE result
END

SELECT CASE 
　　WHEN 1 > 0
　　THEN '1 > 0'
　　WHEN 2 > 0
　　THEN '2 > 0'
　　ELSE '3 > 0'
　　END
->1 > 0

字符串日期转换为日期：

SELECT CAST("2017-08-29" AS DATE);
-> 2017-08-29

SELECT COALESCE(NULL, NULL, NULL, 'runoob.com', NULL, 'google.com');
-> runoob.com

SELECT CONNECTION_ID();
-> 4292835

SELECT CONV(15, 10, 2);
-> 1111

SELECT CHARSET('ABC')
->utf-8    

SELECT CHARSET(CONVERT('ABC' USING gbk))
->gbk

SELECT CURRENT_USER();
-> guest@%

SELECT DATABASE();   
-> runoob

SELECT IF(1 > 0,'正确','错误')    
->正确

SELECT IFNULL(null,'Hello Word')
->Hello Word

SELECT ISNULL(NULL);
->1

SELECT LAST_INSERT_ID();
->6

SELECT NULLIF(25, 25);
->

SELECT SESSION_USER();
-> guest@%

SELECT SYSTEM_USER();
-> guest@%

SELECT USER();
-> guest@%

SELECT VERSION()
-> 5.6.34