I have two SQL tables, and I like to have the result shown below.
table_1
id userId
---------------
1 u1
2 u2
3 u3
4 u4
5 u5
table_2
userId flag
-----------------
u1 1
u4 0
Result I need
id userId flag
------------------------
1 u1 1
2 u2 Null
3 u3 Null
4 u4 0
5 u5 Null
Solution
You can use this following LEFT JOIN for the purpose, It will give all right table data with matched right table data .
SELECT * FROM table_1 LEFT JOIN table_2 on table_1.userId=table_2.userId