How to find sum of multiple columns in a table in SQL Server 2005?

I have a table Emp which has these rows:

Emp_cd | Val1  | Val2  | Val3  | Total
-------+-------+-------+-------+-------
 1     | 1.23  | 2.23  | 3.43  | 
 2     | 23.03 | 12.23 | 2.92  |
 3     | 7.23  | 9.05  | 13.43 |
 4     | 03.21 | 78.23 | 9.43  |

I want to find SUM of Val1, Val2, Val3 and which will show in the Total column.

Easy:

SELECT 
   Val1,
   Val2,
   Val3,
   (Val1 + Val2 + Val3) as 'Total'
FROM Emp

or if you just want one row:

SELECT 
   SUM(Val1) as 'Val1',
   SUM(Val2) as 'Val2',
   SUM(Val3) as 'Val3',
   (SUM(Val1) + SUM(Val2) + SUM(Val3)) as 'Total'
FROM Emp

You must also be aware of null records:

SELECT  (ISNULL(Val1,0) + ISNULL(Val2,0) + ISNULL(Val3,0)) as 'Total'
FROM Emp

Usage of ISNULL:

ISNULL(col_Name, replace value)

Just as a regular SELECT?

SELECT 
   Val1, Val2, Val3,
   Total = Val1 + Val2 + Val3
FROM dbo.Emp

Or do you want to determine that total and update the table with those values?

UPDATE dbo.Emp
SET Total = Val1 + Val2 + Val3

If you want to have this total be current at all times - you should have a computed column in your table:

ALTER TABLE dbo.Emp
ADD CurrentTotal AS Val1 + Val2 + Val3 PERSISTED

Then you will always get the current total - even if the values change:

SELECT 
   Val1, Val2, Val3, CurrentTotal
FROM dbo.Emp

Try this:

select sum(num_tax_amount+num_total_amount) from table_name;

Another example using COALESCE. http://sqlmag.com/t-sql/coalesce-vs-isnull

SELECT (COALESCE(SUM(val1),0) + COALESCE(SUM(val2), 0)
+ COALESCE(SUM(val3), 0) + COALESCE(SUM(val4), 0)) AS 'TOTAL'
FROM Emp

Hi You can use a simple query,

select emp_cd, val1, val2, val3,
(val1+val2+val3) as total 
from emp;

In case you need to insert a new row,

insert into emp select emp_cd, val1, val2, val3,
(val1+val2+val3) as total 
from emp;

In order to update,

update emp set total = val1+val2+val3;

This will update for all comumns

Needed to do similar work on a Postgres db table with null value. Ended up creating a function as there are too COALESCE to add.

CREATE OR REPLACE FUNCTION array_sum_float(float[])
	RETURNS float
AS
$$
DECLARE
	arrInts ALIAS FOR $1;
	sum int DEFAULT 0;
BEGIN
	FOR I IN ARRAY_LOWER(arrInts, 1)..ARRAY_UPPER(arrInts, 1)
		LOOP
			sum = sum + COALESCE(arrInts[I], 0);
		END LOOP;
	RETURN sum;
END;
$$
	LANGUAGE plpgsql;

SELECT array_sum_float(ARRAY [6,8, null, 2]);
SELECT array_sum_float(ARRAY [Val1, Val2, Val3]) from Emp;

SELECT Emp_cd, Val1, Val2, Val3, SUM(Val1 + Val2 + Val3) AS TOTAL 
FROM Emp
GROUP BY Emp_cd, Val1, Val2, Val3

use a trigges it will work:-

->CREATE TRIGGER trigger_name BEFORE INSERT ON table_name

FOR EACH ROW SET NEW.column_name3 = NEW.column_name1 + NEW.column_name2;

this will only work only when you will insert a row in table not when you will be updating your table for such a pupose create another trigger of different name and use UPDATE on the place of INSERT in the above syntax