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https://dev.mysql.com/doc/refman/5.7/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/5.7/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/5.7/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/5.7/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/5.7/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/5.7/en/null-values.html
The NULL value means “no data.” NULL can be written in any lettercase. Treatment of \N as a synonym for NULL in SQL statements is deprecated as of MySQL 5.7.18 and is removed in MySQL 8.0; use NULL instead. Be aware that the NULL value is ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-standard-monitor.html
The contents show which transactions are involved, the statement each was attempting to execute, the locks they have and need, and which transaction InnoDB decided to roll back to break the deadlock. The Lock Monitor is the same as the Standard ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-parameters.html
daemon_memcached_engine_lib_path Command-Line Format --daemon-memcached-engine-lib-path=dir_name System Variable daemon_memcached_engine_lib_path Scope Global Dynamic No Type Directory name Default Value NULL The path of the directory containing the ... System variables that are true or false can be enabled at server startup by naming them, or disabled by using a --skip- ...
https://dev.mysql.com/doc/refman/5.7/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 ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-ndbd-definition.html
Consider this table definition: CREATE TABLE example ( a INT NOT NULL, b INT NOT NULL, c INT NOT NULL, PRIMARY KEY(a), UNIQUE(b) ) ENGINE=NDBCLUSTER; For each record, there are 12 bytes of data plus 12 bytes overhead. The [ndbd] and [ndbd default] ...