MySQL intercepts the string to remove duplication, and MySQL intercepts the string to remove reassembly

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1： String interception

LEFT(guid_,LENGTH(guid_) – 5)//1001-1002-1003 Intercept as 1001-1002

2： Determine whether a string exists

IN(‘1001′,’1002′,’1003’)// where id in(xxxx) You can use a field of the query to directly where id in (select id from xxxx)

3： Repeat according to a certain field

Add to query results COUNT (DISTINCT You want to remove the duplicate according to the field )//select name ,age,sex ,count(distinct name ) from xxx where xxx group by name , age, sex

4： Field splicing

GROUP_CONTACT(name,’:’,sex)//group_contact(‘ Xiao Ming ’,’:’,’ Woman ’)-》“ Xiao Ming ： Woman ”

5： Date format

DATE_FORMAT(date,’%Y-%m-%d’)// 20130806 ->2013-08-06

6： Calling stored procedure

CALL xxxxx

7： conditional case when Use

SELECT CASE WHEN sex = 1 THEN “ male ” WHEN sex = 0 THEN “ Woman ” END AS sex

8： Judgment time range

created_at > SUBDATE(NOW(),INTERVAL 24 HOUR) AND created_at < NOW()//24 Within hours

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