how do i join two different tables in mysql - mysql

Question

This is table1:
id name m1 m2 m3 total itemno
1 raj 10 10 10 30 1
2 ram 60 60 60 180 1
3 kumar 70 70 70 210 1
4 kanna 50 50 50 150 1
5 vivek 64 64 91 200 1
5 vivek 90 90 90 270 2
This is table2:
id name mark1 mark2 mark3 itemno
101 vivek 78 78 78 1
102 vivekkanna 89 88 78 1
103 rajagopalan 97 90 98 1
104 kumar 69 54 56 1
101 vivek 90 90 90 2
I want to join these two tables like this into a result set that looks like this:
id name m1 m2 m3 total mark1 mark2 mark3 item no
1 raj 10 10 10 30 0 0 0 1
2 ram 60 60 60 180 0 0 0 1
3 kumar 70 70 70 210 69 54 56 1
4 kanna 50 50 50 150 0 0 0 1
5 vivek 64 64 91 200 78 78 78 1
5 vivek 90 90 90 270 90 90 90 2

Answer 1

Seems you want a regular LEFT JOIN, returning a default value if the row in table2 does not exist;
SELECT t1.id, t1.name, t1.m1, t1.m2, t1.m3,
COALESCE(t2.mark1, 0) mark1, COALESCE(t2.mark2, 0) mark2, t1.itemno
FROM table1 t1
LEFT JOIN table2 t2 ON t1.name = t2.name AND t1.itemno = t2.itemno
ORDER BY t1.id, t1.itemno
An SQLfiddle to test with
We use a LEFT JOIN to get the default NULL value for all table2 fields that don't match with a row in table1, then COALESCE to turn them into 0 instead.