Using 'TRUE' and 'FALSE' For Bit Types In SQL Server

SQL Server, as you are no doubt aware, has a type that can be used to represent boolean states - true and false.

This type is called BIT

true is represented as 1, and false as 0.

Like so:

DECLARE @IsDaylight BIT = 1;
DECLARE @IsNightTime BIT = 0;

SELECT
    @IsDaylight  IsDayLight,
    @IsNightTime IsNightTime;

If you run this it will print the following:

IsDayLight	IsNightTime
1	0

What you might not know is that you can use strings to represent true and false values.

SET @IsDaylight = 'FALSE';
SET @IsNightTime = 'TRUE';

SELECT
    @IsDaylight  IsDayLight,
    @IsNightTime IsNightTime;

The strings have to be the values ‘True’ or ‘False’ (not case sensitive). Any other values will give you an error.

I think this is easier to read than 0 or 1.

Running the script will return the following:

IsDayLight	IsNightTime
0	1

Another interesting thing to note - any value that is not 0 is considered true, including negative numbers.

SET @IsDaylight = 2

SELECT
    @IsDaylight IsDayLight;

SET @IsDaylight = -1;
SELECT
    @IsDaylight IsDayLight;

This script will print the following:

IsDayLight
1

IsDayLight
1

Happy hacking!