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https://dev.mysql.com/doc/refman/5.7/en/gis-wkt-functions.html
If the geometry argument is NULL or not a syntactically well-formed geometry, or if the SRID argument is NULL, the return value is NULL. If the geometry argument is NULL or not a syntactically well-formed geometry, or if the SRID argument is NULL, ... These functions take as arguments a Well-Known Text (WKT) representation and, optionally, a spatial reference system identifier ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-replication-conflict-resolution.html
(An example that uses NDB$OLD() with an exceptions table is shown later in this section.) Additional columns may optionally be defined following the copied primary key columns, but not before any of them; any such extra columns cannot be NOT NULL.
https://dev.mysql.com/doc/refman/5.7/en/information-functions.html
The result value is 0, or NULL for inappropriate arguments such as a NULL or negative repeat count. mysql> SELECT DATABASE(); -> 'test' If there is no default database, DATABASE() returns NULL. The value of LAST_INSERT_ID() is not changed if you set ...It may be used to time how quickly MySQL processes the ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-information-schema-fulltext_index-tables.html
When OPTIMIZE TABLE is run, the INNODB_FT_BEING_DELETED table is emptied, and DOC_ID values are removed from the INNODB_FT_DELETED table. INNODB_FT_BEING_DELETED: Provides a snapshot of the INNODB_FT_DELETED table; it is used only during an OPTIMIZE ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-online-ddl-operations.html
ALGORITHM=INPLACE is not permitted under certain conditions if columns have to be converted to NOT NULL. For a PRIMARY KEY index, MySQL also checks that none of the PRIMARY KEY columns contains a NULL. When you add a primary key using the ... Online ...
https://dev.mysql.com/doc/refman/5.7/en/index-statistics.html
For a join based on the <=> comparison operator, NULL is not treated differently from any other value: NULL <=> NULL, just as N <=> N for any other N. However, for a join based on the = operator, NULL is different from non-NULL values: expr1 = expr2 ... Storage engines collect statistics about tables for use by the ...
https://dev.mysql.com/doc/refman/5.7/en/mathematical-functions.html
ABS(X) Returns the absolute value of X, or NULL if X is NULL. Returns NULL if X is not in the range -1 to 1. mysql> SELECT ACOS(1); -> 0 mysql> SELECT ACOS(1.0001); -> NULL mysql> SELECT ACOS(0); -> 1.5707963267949 ASIN(X) Returns the arc sine of X, ...An implication of this is that ABS(-9223372036854775808) produces an error because the result cannot be stored in a signed BIGINT ...
https://dev.mysql.com/doc/refman/5.7/en/myisamchk-table-info.html
Nullpos, Nullbit For columns that can be NULL, MyISAM stores NULL values as a flag in a byte. Depending on how many nullable columns there are, there can be one or more bytes used for this purpose. The Nullpos and Nullbit values, if nonempty, ... To ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-ndb-transid-mysql-connection-map-table.html
The ndb_transid_mysql_connection_map table provides a mapping between NDB transactions, NDB transaction coordinators, and MySQL Servers attached to an NDB Cluster as API nodes. This information is used when populating the server_operations and ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-information-schema-examples.html
Identifying Blocking Transactions It is sometimes helpful to identify which transaction blocks another. The tables that contain information about InnoDB transactions and data locks enable you to determine which transaction is waiting for another, ...