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how to subtract two values in sql from the multiple table for example we subtract two values in same table table Name=tbl1 and fields are a=column1 and b=column2
like =sum as column1-column2
Now my question is that how to subtract the two values from different column
example i have two table table1=tbl1 and table2=tbl2
in tbl1 i have column A,b &
in tbl2 i have column c

now i want thing like this= c as tbl1.a-tbl1.b
Posted
phil.o 30-Sep-15 15:27pm
What have you tried?

## Solution 1

If I understand your question correctly, you need to create a query where you join the tables. After doing that you can do the calculation.

Consider the following example
SQL
```SELECT t1.A,
t1.B,
t2.C,
t1.A - t1.B - t2.C AS Calculation
FROM Table1 t1 INNER JOIN Table2 t2
ON t1.ParentColumn = t2.ChildColumn```

If this is to be an update situation for for example Table1.D then consider the following example
SQL
```UPDATE t1
SET D = t1.A - t1.B - t2.C
FROM Table1 t1 INNER JOIN Table2 t2
ON t1.ParentColumn = t2.ChildColumn```

For info about using joins in update statements, see UPDATE[^]
Another variation could be for example
SQL
```UPDATE Table1
SET D = (SELECT Table1.A - Table1.B - t2.C
FROM Table2 t2
WHERE Table1.ParentColumn = t2.ChildColumn)```

Note that this must return only one value per each row in Table1 so if the relation is one-to-many you need to restrict the query or use aggregates such as SUM

v3
Member 11963532 30-Sep-15 15:28pm
and how to update the result in tbl1 field c
Wendelius 30-Sep-15 15:34pm
Have a look at the updated solution
Member 11963532 30-Sep-15 15:37pm
thank you soo much Mr Mika Wendelius you always help me thnx for thaat again and again and lottttsss
Member 11963532 30-Sep-15 16:07pm
bro its can't be update because the first table column field is competed and the error is showing like this,,,,
The column "remaing_income" cannot be modified because it is either a computed column or is the result of a UNION operator.
Member 11963532 30-Sep-15 16:08pm
bro Mika Wendelius its can't be update because the first table column field is competed and the error is showing like this,,,,
The column "remaing_income" cannot be modified because it is either a computed column or is the result of a UNION operator.