Convert negative data into positive data in SQL Server

Question

You are thinking in the function ABS, that gives you the absolute value of numeric data.

SELECT ABS(a) AS AbsoluteA, ABS(b) AS AbsoluteB
FROM YourTable

The best solution is: from positive to negative or from negative to positive

For negative:

SELECT ABS(a) * -1 AS AbsoluteA, ABS(b) * -1 AS AbsoluteB
FROM YourTable

For positive:

SELECT ABS(a) AS AbsoluteA, ABS(b)  AS AbsoluteB
FROM YourTable

UPDATE mytbl
SET a = ABS(a)
where a < 0

Use the absolute value function ABS. The syntax is

ABS ( numeric_expression )

An easy and straightforward solution using the CASE function:

SELECT CASE WHEN ( a > 0 ) THEN (a*-1) ELSE (a*-1) END AS NegativeA,
       CASE WHEN ( b > 0 ) THEN (b*-1) ELSE (b*-1) END AS PositiveB
FROM YourTableName