MySQL multi-table association one-to-many query to get the latest data

Scenario: Individual users perform real-name authentication.There are multiple real-name authentication results for one person.Expect to get the latest real-name authentication result plus personal information for each person.

1. Write the sql for querying user information and real-name authentication

SELECT*FROMUSERS uLEFT JOIN USER_AUTH ua ON ua.userId = u.id

Second, the latest real-name record can be obtained by transforming sql

Method one:

1. The general idea is to perform a left join to obtain this table in advance and filter out the latest record by grouping.

SELECT*FROMUSERS uLEFT JOIN ( SELECT MAX( id ) AS id, userId FROM USER_AUTH GROUP BY userId ) AS ua ON ua.userId = u.id

Method 2:

Connect the table first, then take out the first one

SELECT*FROM(SELECTu.id,row_number() over ( PARTITION BY u.id ORDER BY u.id ) AS rownoFROMUSERS uLEFT JOIN USER_AUTH ua ON u.id = ua.userId) tmpWHERErowno = 1;

Method three:

SELECTu.idFROMUSERS uLEFT JOIN USER_AUTH ua ON ua.id = (SELECT b.id FROM USER_AUTH b WHERE b.userId = u.id HAVING 1 ORDER BY b.id )

sql server needs to cache the following wording

The difference is that subquery order by needs to use top

SELECTu.idFROMUSERS uLEFT JOIN USER_AUTH ua ON ua.id = (SELECT top 1 b.id FROM USER_AUTH b WHERE b.userId = u.id ORDER BY b.id )

DataGrip Appeal method mysql results:

Navicat Premium 15 mysql execution result

Navicat Premium 15 SQL server execution result

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sql is executed multiple times and found that the time is not stable.Taken together Method 1 is more efficient

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