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https://dev.mysql.com/doc/refman/8.0/en/replication-features-row-searches.html
A unique index where every column in the index has a NOT NULL attribute. If the algorithm is able to select a primary key or a unique index where every column in the index has a NOT NULL attribute, it uses this index to iterate over the rows in the ... When a replica using row-based replication format applies an UPDATE or DELETE operation, it must search the relevant table for the matching ...
https://dev.mysql.com/doc/refman/8.0/en/row-constructor-optimization.html
row *************************** id: 1 select_type: SIMPLE table: t1 partitions: NULL type: ref possible_keys: PRIMARY key: PRIMARY key_len: 4 ref: const rows: 3 filtered: 100.00 Extra: Using where In such cases, rewriting the row constructor ...For ...
https://dev.mysql.com/doc/refman/8.0/en/set.html
For example, a column specified as SET('one', 'two') NOT NULL can have any of these values: '' 'one' 'two' 'one,two' A SET column can have a maximum of 64 distinct members. A SET is a string object that can have zero or more values, each of which ...
https://dev.mysql.com/doc/refman/8.0/en/spatial-geohash-functions.html
Unless otherwise specified, functions in this section handle their geometry arguments as follows: If any argument is NULL, the return value is NULL. Geohash is a system for encoding latitude and longitude coordinates of arbitrary precision into a ...
https://dev.mysql.com/doc/refman/8.0/en/string-type-syntax.html
CHAR(0) is also quite nice when you need a column that can take only two values: A column that is defined as CHAR(0) NULL occupies only one bit and can take only the values NULL and '' (the empty string). A string object that can have only one ...
https://dev.mysql.com/doc/refman/8.0/en/sys-innodb-lock-waits.html
locked_table_partition The name of the locked partition, if any; NULL otherwise. locked_table_subpartition The name of the locked subpartition, if any; NULL otherwise. This field reports NULL if the session that issued the blocking query becomes ...
https://dev.mysql.com/doc/refman/8.0/en/sys-ps-is-consumer-enabled.html
Returns YES or NO to indicate whether a given Performance Schema consumer is enabled, or NULL if the argument is NULL. (Prior to MySQL 8.0.18, the function returns NULL if the argument is not a valid consumer name.) This function accounts for the ...If the argument is not a valid consumer name, an error ...
https://dev.mysql.com/doc/refman/8.0/en/system-schema.html
row *************************** CATALOG_NAME: def SCHEMA_NAME: mysql DEFAULT_CHARACTER_SET_NAME: utf8mb4 DEFAULT_COLLATION_NAME: utf8mb4_0900_ai_ci SQL_PATH: NULL DEFAULT_ENCRYPTION: NO *************************** 2. row *************************** ...It contains tables that store information required by the MySQL server as it ...
https://dev.mysql.com/doc/refman/8.0/en/where-optimization.html
This is also done for any NOT NULL expression when used with only one table. A table that is used with a WHERE clause on a PRIMARY KEY or a UNIQUE index, where all index parts are compared to constant expressions and are defined as NOT NULL. This ...
https://dev.mysql.com/doc/refman/8.0/en/arithmetic-functions.html
(See Section 13.1, “Numeric Data Types”.) / Division: mysql> SELECT 3/5; -> 0.60 Division by zero produces a NULL result: mysql> SELECT 102/(1-1); -> NULL A division is calculated with BIGINT arithmetic only if performed in a context where its ... Table 14.9 Arithmetic Operators Name Description %, MOD Modulo operator * Multiplication operator + Addition operator - Minus operator - Change the sign of the argument / Division operator DIV Integer division The usual arithmetic operators are ...