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https://dev.mysql.com/doc/refman/5.7/en/outer-join-simplification.html
Instead, MySQL converts the query to a query with no outer join operation if the WHERE condition is null-rejected. (That is, it converts the outer join to an inner join.) A condition is said to be null-rejected for an outer join operation if it ...
https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html
GROUP_CONCAT(expr) This function returns a string result with the concatenated non-NULL values from a group. For information about a change in MySQL 8.0 that permits bit operations to take binary string type arguments (BINARY, VARBINARY, and the ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-replication-conflict-resolution.html
The name of this table is that of the table for which conflict resolution is to be applied, with the string $EX appended. (An example that uses NDB$OLD() with an exceptions table is shown later in this section.) Additional columns may optionally be ... Requirements Source Column Control Conflict Resolution Control Conflict Resolution Functions Conflict Resolution Exceptions Table Conflict Detection Status Variables Examples When using a replication setup involving multiple sources (including circular replication), it is possible that different sources may try to update the same row on the replica with different ...
https://dev.mysql.com/doc/refman/5.7/en/gis-wkt-functions.html
LineFromText(wkt [, srid]), LineStringFromText(wkt [, srid]) ST_LineFromText(), ST_LineStringFromText(), LineFromText(), and LineStringFromText() are synonyms. LineFromText() and LineStringFromText() are deprecated; expect them to be removed in a ...
https://dev.mysql.com/doc/refman/5.7/en/myisamchk-table-info.html
For strings, it may be shorter than the full length of the indexed column, because you can index a prefix of a string column. Nullpos, Nullbit For columns that can be NULL, MyISAM stores NULL values as a flag in a byte. Depending on how many ... To ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-online-ddl-operations.html
When you add a primary key using the ALGORITHM=COPY clause, MySQL converts NULL values in the associated columns to default values: 0 for numbers, an empty string for character-based columns and BLOBs, and 0000-00-00 00:00:00 for DATETIME. Online ...
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 CHARSET('abc'); -> 'latin1' mysql> SELECT CHARSET(CONVERT('abc' USING utf8)); -> 'utf8' mysql> SELECT CHARSET(USER()); -> 'utf8' ...It ...
https://dev.mysql.com/doc/refman/5.7/en/show-slave-status.html
In MySQL 5.7, this field is NULL (undefined or unknown) if the replica SQL thread is not running, or if the SQL thread has consumed all of the relay log and the replica I/O thread is not running. (In older versions of MySQL, this field was NULL if ... SHOW SLAVE STATUS [FOR CHANNEL channel] This statement provides status information on essential parameters of the replica ...
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/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 ...