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https://dev.mysql.com/doc/refman/8.4/en/partitioning-handling-nulls.html
Partitioning in MySQL does nothing to disallow NULL as the value of a partitioning expression, whether it is a column value or the value of a user-supplied expression. Even though it is permitted to use NULL as the value of an expression that must ...
https://dev.mysql.com/doc/refman/8.4/en/working-with-null.html
The NULL value can be surprising until you get used to it. Conceptually, NULL means “a missing unknown value” and it is treated somewhat differently from other values. In MySQL, 0 or NULL means false and anything else means true. This special ...
https://dev.mysql.com/doc/refman/8.4/en/problems-with-null.html
The concept of the NULL value is a common source of confusion for newcomers to SQL, who often think that NULL is the same thing as an empty string ''. For example, the following statements are completely different: mysql> INSERT INTO my_table ...
https://dev.mysql.com/doc/refman/8.4/en/is-null-optimization.html
MySQL can perform the same optimization on col_name IS NULL that it can use for col_name = constant_value. For example, MySQL can use indexes and ranges to search for NULL with IS NULL. This optimization does not occur in cases when the column ...
https://dev.mysql.com/doc/internals/en/null-bitmap.html
The binary protocol sends NULL values as bits inside a bitmap instead of a full byte as the ProtocolText::ResultsetRow does. If many NULL values are sent, it is more efficient than the old way. Caution For the Binary Protocol Resultset Row the ...
https://dev.mysql.com/doc/internals/en/optimizer-early-nulls-filtering.html
Suppose we have a join order such as this one: ..., tblX, ..., tblY, ... Suppose further that table tblY is accessed via ref or eq_ref access on tblY.key_column = tblX.column or, in the case of ref access using multiple key parts, via ... Here the ...
https://dev.mysql.com/doc/refman/8.4/en/null-values.html
The NULL value means “no data.” NULL can be written in any lettercase. Be aware that the NULL value is different from values such as 0 for numeric types or the empty string for string types. For text file import or export operations performed ...
https://dev.mysql.com/doc/connectors/en/connector-net-programming-datetime-null.html
As such, when assigning values from a query to a DateTime variable, you must first check whether the value is in fact NULL.
https://dev.mysql.com/doc/connector-net/en/connector-net-programming-datetime-null.html
As such, when assigning values from a query to a DateTime variable, you must first check whether the value is in fact NULL.
https://dev.mysql.com/doc/internals/en/optimizer-late-nulls-filtering.html
Suppose we have a query plan with table tblX being accessed via the ref access method: tblX.key_part1 = expr1 AND tblX.key_part2 = expr2 AND ... Before performing an index lookup, we determine whether any of the expri values is NULL. If it is, we ...