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https://dev.mysql.com/doc/refman/8.0/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 ...We can verify this behavior by examining the effects on the file system of creating a table partitioned by HASH and populating it with a record containing appropriate ...
https://dev.mysql.com/doc/refman/8.0/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/8.0/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/8.0/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/refman/8.0/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 sorting with ORDER BY, NULL values sort before ...
https://dev.mysql.com/doc/refman/8.0/en/date-and-time-functions.html
For example: mysql> SELECT DAYOFMONTH('2001-11-00'), MONTH('2005-00-00'); -> 0, 0 Other functions expect complete dates and return NULL for incomplete dates. For example: mysql> SELECT DATE_ADD('2006-05-00',INTERVAL 1 DAY); -> NULL mysql> SELECT ...
https://dev.mysql.com/doc/refman/8.0/en/string-functions.html
Also, if strict SQL mode is enabled, the result from CHAR() becomes NULL. mysql> SELECT CONCAT_WS(',', 'First name', 'Second name', 'Last Name'); -> 'First name,Second name,Last Name' mysql> SELECT CONCAT_WS(',', 'First name', NULL, 'Last Name'); -> ...For functions that operate on string positions, the first position is ...
https://dev.mysql.com/doc/refman/8.0/en/group-by-modifiers.html
These rows have the country and products columns set to NULL. This row has the year, country, and products columns set to NULL. The NULL indicators in each super-aggregate row are produced when the row is sent to the client. For any column in the ...
https://dev.mysql.com/doc/refman/8.0/en/switchable-optimizations.html
(Depending on the nullability of the derived table, this can sometimes be simplified further to an inner join.) This can be done for a subquery which meets the following conditions: The subquery does not make use of any nondeterministic functions, ...Its value is a set of flags, each of which has a value of on or off to indicate whether the corresponding optimizer behavior is enabled or ...
https://dev.mysql.com/doc/refman/8.0/en/miscellaneous-functions.html
There are multiple ways to cause MySQL to accept the query: Alter the table to make name a primary key or a unique NOT NULL column. (This technique is inapplicable if NULL must be permitted as a valid name value.) Use ANY_VALUE() to refer to ...The ...