MySQL - results from 'SELECT WHERE STH' and 'SELECT WHERE NOT STH' don't sum to full table

How is that possible that result开发者_StackOverflow中文版s from those 2 queries:

SELECT * FROM `workers` WHERE `name` = 'Smith`

and

SELECT * FROM `workers` WHERE NOT `name` = 'Smith`

doesn't sum to whole table workers?

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Because NULL in name field does not get into either query.

In ternary logic which SQL uses, NULL = 'Smith' and NOT NULL = 'Smith' both evaluate to NULL and are filtered out.

Use NULL-safe comparison operator, <=>:

SELECT * FROM `workers` WHERE `name` <=> 'Smith`

and

SELECT * FROM `workers` WHERE NOT `name` <=> 'Smith`