update data from another table postgresql using IN

Question

I have 2 tables :table1 and table2.When using this query,

SELECT * 
FROM table1 a 
WHERE a.name IN (SELECT name FROM table2 )

The result is 20.

When I want update data based on this query

UPDATE table1 SET number='1' 
FROM table1 a 
WHERE a.name IN (SELECT name FROM table2)

The result is all the number will be set to 1 instead of only 20.The default number is 0.

Answer 1

Try this

UPDATE table1 t1 SET number=1
JOIN table2 t2 ON t1.name = t2.name