Database synchronization Optimization Skills Sharing _ Database Other

Scenario 1: You need to sync some of the fields of a table to some fields in another table.

INSERT into table1 (a,b,c,d)
select
a,b,c,d to Table2
where not EXISTS (SELECT * FROM table1 where table2. ' A ' =table1. ' B ')
;

Skips when the last subquery exists.

Scenario 2: A new field in the table needs to be recalculated and updated to the table.

If you go with the foot, do not use the transaction can only update 10 or so, if there is a corresponding algorithm, you can first generate the UPDATE statement, and then update.

Scenario 3 Association tables, a table field to batch update

UPDATE Oto_payment as a INNER JOIN Oto_customer as C on A.openid=c.openid
SET a.customer_id=c.customer_id;