https://dev.mysql.com/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/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/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/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/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/null-mysql-store-result.html
It is possible for mysql_store_result() to return NULL following a successful call to mysql_query(). When this happens, it means one of the following conditions occurred: There was a malloc() failure (for example, if the result set was too large).
https://dev.mysql.com/group-by-modifiers.html
The GROUP BY clause permits a WITH ROLLUP modifier that causes summary output to include extra rows that represent higher-level (that is, super-aggregate) summary operations. ROLLUP thus enables you to answer questions at multiple levels of ...
https://dev.mysql.com/create-index.html
CREATE [UNIQUE | FULLTEXT | SPATIAL] INDEX index_name [index_type] ON tbl_name (key_part,...) [index_option] [algorithm_option | lock_option] ... This guideline is especially important for InnoDB tables, where the primary key determines the ...
https://dev.mysql.com/miscellaneous-functions.html
The function return value and type are the same as the return value and type of its argument, but the function result is not checked for the ONLY_FULL_GROUP_BY SQL mode. As a result, the address value for rows within each name group is ...
https://dev.mysql.com/comparison-operators.html
Whether a value is not within a range of values !=, <> Not equal operator NOT IN() Whether a value is not within a set of values NOT LIKE Negation of simple pattern matching STRCMP() Compare two strings Comparison operations result in a value of 1 ...
