左联接后更新行

Question

I'm looking for a way to update some values in a table if they were used in a left join.

I have two tables:

table1:
id | name | age | job
1  | john | 31  | 
2  | eric | 25  | 

table2:
id | job | inserted
1  | lawyer | 0
2  | dentist | 1
3  | cop    |  0

Then I run the query:

UPDATE  table1
LEFT JOIN
        table2
ON      table1.id = table2.id
SET     table1.job = `table2.job`
WHERE   table2.inserted = 0

But I want to update the rows from table2 that were used in the update so they have inserted = 1. This for two reasons 1) to speed up the join and 2) so I can check which rows of table2 were not used. (The inserts in table2 happen before table1 , but the id s in table2 should always be present in table1 if all cron jobs run okay.)

Answer 1

You shouldn't be using a LEFT JOIN , since you only want to update rows in table1 that have a matching row in table2 . Try:

UPDATE table1 AS t1
JOIN table2 AS t2 ON t1.id = t2.id
SET t1.job = t2.job, t2.inserted = 1
WHERE t2.inserted = 0

DEMO