A few questions about NULL?

Question

MySQL

1) NULL when compared with any type returns NULL?
2) NULL is evaluated as false?
3) Why can't you directly compare with NULL (myfield = NULL), but use IS NULL / IS NOT NULL? Why such logic?

Answer 1

1) When using operators =, <, >, <>- yes
2) No. But at the same time it is not true, i.e. when used in WHERE or JOIN, the condition with it will work as false. Well, outside the database, for example, in PHP and other weakly typed languages, it easily turns into false
3) Some kind of strange question, inverted. The IS NULL / IS NOT NULL operators were invented because the comparison with NULL ordinary operators does not work the way everyone is used to. In general, in SQL ternary logic (for example =):

=     | TRUE    FALSE   NULL
________________________________
TRUE  | TRUE    FALSE   NULL
FALSE | FALSE   TRUE    NULL
NULL  | NULL    NULL    NULL