Help needed to merge values from two tables -

Question

We have these three test tables shown, which have a common ID; And amount fields; I want the -------
test1.val = test2.val + test3.val
when they have common ids in them;
I have shown the test data below: And the expected output;
NOTE: In database with real table values - each of them have millions of rows in them. So effeciency is very important here;
SQL> desc test1;
Name Null? Type
ID NUMBER
VAL NUMBER
SQL> desc test2;
Name Null? Type
ID NUMBER
VAL NUMBER
SQL> desc test3;
Name Null? Type
ID NUMBER
VAL NUMBER
SQL> select * from test1;
ID VAL
1 50
2 50
3 55
4 60
5 20
5 rows selected.
SQL> select * from test2;
ID VAL
1 25
1 25
2 5
2 5
4 75
5 rows selected.
SQL> select * from test3;
ID VAL
1 25
1 25
2 5
2 25
2 25
5 10
6 rows selected.
I EXPECT the output to be:
SQL> select * from test1;
ID VAL
1 100
2 65
3 20
4 75
3 20
5 10
6 rows selected.

Answer 1

Need help with the update queries - joining three tables -