Why is null=null in mysql false?

Question

Why does SELECT IF(null=null, 'true', 'false'); return false but SELECT IF(1=1, 'true', 'false'); return true in mysql?

@axiac Thanks about that. I encountered that because in a programming language e.g python, it's true — Wafula Samuel
– Wafula Samuel, Commented Dec 9, 2018 at 15:21

axiac · Accepted Answer · 2018-12-09 15:21:51Z

2

NULL in SQL is a placeholder for an unknown value. Because it is unknown it cannot be compared to other values, not even with NULL.

Read "unknown" every time you encounter NULL in a query and it will make more sense.

Regarding MySQL, the behaviour of NULL is documented: https://dev.mysql.com/doc/refman/5.7/en/working-with-null.html

answered Dec 9, 2018 at 15:21

axiac

73.4k11 gold badges120 silver badges150 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Wafula Samuel Over a year ago

it was indeed surprising as mentioned in the documentation 😂. Thanks though

axiac Over a year ago

The programming languages that provide the concept of NULL give it a different semantic. In such languages NULL is equal to NULL and in some of them (PHP, JavaScript etc.) it is even equal to 0 or ''.

Collectives™ on Stack Overflow

Why is null=null in mysql false?

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related