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https://dev.mysql.com/doc/refman/8.4/en/checksum-table.html
If you run CHECKSUM TABLE against a view, the Checksum value is always NULL, and a warning is returned. For a nonexistent table, CHECKSUM TABLE returns NULL and generates a warning. If the table does not meet all these conditions, the QUICK method ...[QUICK | EXTENDED] CHECKSUM TABLE reports a checksum for the contents of a ...
https://dev.mysql.com/doc/refman/8.4/en/descending-indexes.html
MySQL supports descending indexes: DESC in an index definition is no longer ignored but causes storage of key values in descending order. Previously, indexes could be scanned in reverse order but at a performance penalty. A descending index can be ...
https://dev.mysql.com/doc/refman/8.4/en/examples.html
Here are examples of how to solve some common problems with MySQL. Some of the examples use the table shop to hold the price of each article (item number) for certain traders (dealers). Supposing that each trader has a single fixed price per ...
https://dev.mysql.com/doc/refman/8.4/en/functions.html
Expressions can be written using values from several sources, such as literal values, column values, NULL, variables, built-in functions and operators, loadable functions, and stored functions (a type of stored object). An expression that contains ... Expressions can be used at several points in SQL statements, such as in the ORDER BY or HAVING clauses of SELECT statements, in the WHERE clause of a SELECT, DELETE, or UPDATE statement, or in SET ...
https://dev.mysql.com/doc/refman/8.4/en/gis-point-property-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. A Point consists of X and Y coordinates, which may be obtained using the ST_X() and ST_Y() ...
https://dev.mysql.com/doc/refman/8.4/en/index-extensions.html
Consider this table definition: CREATE TABLE t1 ( i1 INT NOT NULL DEFAULT 0, i2 INT NOT NULL DEFAULT 0, d DATE DEFAULT NULL, PRIMARY KEY (i1, i2), INDEX k_d (d) ) ENGINE = InnoDB; This table defines the primary key on columns (i1, i2). InnoDB ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-innodb-buffer-page-table.html
The column is NULL if the server has not yet accessed the table. The INNODB_BUFFER_PAGE table provides information about each page in the InnoDB buffer pool. For related usage information and examples, see Section 17.15.5, “InnoDB ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-key-column-usage-table.html
This table provides no information about functional key parts because they are expressions and the table provides information only about columns. The KEY_COLUMN_USAGE table has these columns: CONSTRAINT_CATALOG The name of the catalog to which the ...
https://dev.mysql.com/doc/refman/8.4/en/information-schema-optimization.html
row *************************** id: 1 select_type: SIMPLE table: cs partitions: NULL type: const possible_keys: PRIMARY,name key: name key_len: 194 ref: const rows: 1 filtered: 100.00 Extra: Using index *************************** 2. row ...
https://dev.mysql.com/doc/refman/8.4/en/multiple-column-indexes.html
MySQL can create composite indexes (that is, indexes on multiple columns). For certain data types, you can index a prefix of the column (see Section 10.3.5, “Column Indexes”). MySQL can use multiple-column indexes for queries that test all the ...