MySQL IS Operator

The MySQL IS operator tests an expression against TRUE, FALSE, or UNKNOWN. In MySQL, zero is false, any nonzero non-NULL numeric value is true, and NULL represents unknown.

SELECT 1 IS TRUE, 0 IS FALSE, NULL IS UNKNOWN;

Reading Boolean-style TINYINT data

The sample plus2_boolean table stores integer values. IS TRUE matches nonzero, non-NULL values.

SELECT * FROM `plus2_boolean` WHERE mar IS TRUE;

IS NOT TRUE

SELECT * FROM `plus2_boolean` WHERE jan IS NOT TRUE;

Output:

IS NOT TRUE includes both false values and NULL values.

IS UNKNOWN

SELECT * FROM `plus2_boolean` WHERE jan IS UNKNOWN;

Output:

IS UNKNOWN is true only when the expression is NULL. See also NULL handling and the comparison operators.

Using IS with character columns

MySQL can coerce strings to numbers in Boolean contexts. That behavior is demonstrated below, but application queries should normally compare character data explicitly instead of depending on numeric coercion.

SELECT * FROM student3 WHERE class IS TRUE;

Output:

A numeric-looking value such as '5' can evaluate as true after conversion.

SELECT * FROM student3 WHERE class IS FALSE;

Non-numeric text converts differently from meaningful Boolean data, which is why explicit comparisons are clearer.

SELECT * FROM student3 WHERE class IS UNKNOWN;

Output:

This returns rows where class is NULL.

Checkbox matrix example using Boolean data

Sample table

The original student3 SQL dump is retained below for testing.

For conditional output and NULL fallback, see IF(), COALESCE(), and CASE and summing multiple columns.

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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