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https://dev.mysql.com/doc/refman/5.7/en/optimizing-innodb-queries.html
If an indexed column cannot contain any NULL values, declare it as NOT NULL when you create the table. The optimizer can better determine which index is most effective to use for a query, when it knows whether each column contains NULL values. To ...
https://dev.mysql.com/doc/refman/5.7/en/partitioning-linear-hash.html
MySQL also supports linear hashing, which differs from regular hashing in that linear hashing utilizes a linear powers-of-two algorithm whereas regular hashing employs the modulus of the hashing function's value. We call this value V; it can be ...
https://dev.mysql.com/doc/refman/5.7/en/partitioning-overview.html
This section provides a conceptual overview of partitioning in MySQL 5.7. For information on partitioning restrictions and feature limitations, see Section 22.6, “Restrictions and Limitations on Partitioning”. The SQL standard does not provide ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-prepared-statements-instances-table.html
OWNER_OBJECT_TYPE, OWNER_OBJECT_SCHEMA, OWNER_OBJECT_NAME For a prepared statement created by a client session, these columns are NULL. These columns can be used to find stored programs that leak prepared statements: SELECT OWNER_OBJECT_TYPE, ...
https://dev.mysql.com/doc/refman/5.7/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/5.7/en/show-create-table.html
row *************************** Table: t Create Table: CREATE TABLE `t` ( `id` int(11) NOT NULL AUTO_INCREMENT, `s` char(60) DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 SHOW CREATE TABLE quotes table and column names ...
https://dev.mysql.com/doc/refman/5.7/en/spatial-type-overview.html
Some spatial data types hold single geometry values: GEOMETRY POINT LINESTRING POLYGON GEOMETRY can store geometry values of any type. The other single-value types (POINT, LINESTRING, and POLYGON) restrict their values to a particular geometry type.
https://dev.mysql.com/doc/refman/5.7/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 5.7.28, 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/5.7/en/arithmetic-functions.html
If any of the operands of a +, -, /, *, % is a real or string value, the precision of the result is the precision of the operand with the maximum precision. (See Section 11.1, “Numeric Data Types”.) / Division: mysql> SELECT 3/5; -> 0.60 ...
https://dev.mysql.com/doc/refman/5.7/en/date-and-time-types.html
To convert strings in other orders to year-month-day order, the STR_TO_DATE() function may be useful. MySQL permits you to store a “zero” value of '0000-00-00' as a “dummy date.” In some cases, this is more convenient than using NULL values, ... The date and time data types for representing temporal values are DATE, TIME, DATETIME, TIMESTAMP, and ...