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https://dev.mysql.com/doc/refman/5.7/en/show-table-status.html
SHOW TABLE STATUS output has these columns: Name The name of the table. (In-memory data resource usage is reported by the Data_length column.) For partitioned tables, this value is only an estimate and may not be absolutely correct. The Update_time ... SHOW TABLE STATUS [{FROM | IN} db_name] [LIKE 'pattern' | WHERE expr] SHOW TABLE STATUS works likes SHOW TABLES, but provides a lot of information about each non-TEMPORARY ...
https://dev.mysql.com/doc/refman/5.7/en/account-upgrades.html
The MySQL server authenticates connection attempts for each account listed in the mysql.user system table using the authentication plugin named in the plugin column. If the plugin column is empty, the server authenticates the account as follows: ...
https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html
For MyISAM tables, COUNT(*) is optimized to return very quickly if the SELECT retrieves from one table, no other columns are retrieved, and there is no WHERE clause. COUNT(1) is only subject to the same optimization if the first column is defined as ... This section describes aggregate functions that operate on sets of ...
https://dev.mysql.com/doc/refman/5.7/en/features.html
Support for aliases on tables and columns as required by standard SQL. Each index may consist of 1 to 16 columns or parts of columns. An index may use a prefix of a column for CHAR, VARCHAR, BLOB, or TEXT column types. For example, the Scandinavian ... This section describes some of the important characteristics of the MySQL Database ...
https://dev.mysql.com/doc/refman/5.7/en/fulltext-restrictions.html
Although FULLTEXT indexes on ucs2 columns cannot be used, you can perform IN BOOLEAN MODE searches on a ucs2 column that has no such index. Although the use of multiple character sets within a single table is supported, all columns in a FULLTEXT ...
https://dev.mysql.com/doc/refman/5.7/en/get-diagnostics.html
Within a stored procedure p(), we attempt to insert two values into a table that contains a TEXT NOT NULL column. The column prohibits NULL values, so the first insert succeeds but the second causes an exception. GET [CURRENT | STACKED] DIAGNOSTICS ...
https://dev.mysql.com/doc/refman/5.7/en/index-extensions.html
InnoDB automatically extends each secondary index by appending the primary key columns to it. 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 ...This can result in more efficient query execution plans and better ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-innodb-lock-waits-table.html
The INNODB_LOCK_WAITS table has these columns: REQUESTING_TRX_ID The ID of the requesting (blocked) transaction. To obtain details about the lock, join this column with the LOCK_ID column of the INNODB_LOCKS table. To obtain details about the lock, ... The INNODB_LOCK_WAITS table contains one or more rows for each blocked InnoDB transaction, indicating the lock it has requested and any locks that are blocking that ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-innodb-sys-fields-table.html
The INNODB_SYS_FIELDS table provides metadata about the key columns (fields) of InnoDB indexes, equivalent to the information from the SYS_FIELDS table in the InnoDB data dictionary. The INNODB_SYS_FIELDS table has these columns: INDEX_ID An ...For ...
https://dev.mysql.com/doc/refman/5.7/en/information-schema-innodb-sys-tablestats-table.html
Table statistics are updated only for DELETE or UPDATE operations that modify indexed columns. Statistics are not updated by operations that modify only nonindexed columns. ANALYZE TABLE clears table statistics and sets the STATS_INITIALIZED column ... The INNODB_SYS_TABLESTATS table provides a view of low-level status information about InnoDB ...