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https://dev.mysql.com/doc/refman/5.7/en/example-foreign-keys.html
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. A foreign key relationship involves a parent table that holds the initial column ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-locking.html
Shared and Exclusive Locks Intention Locks Record Locks Gap Locks Next-Key Locks Insert Intention Locks AUTO-INC Locks Predicate Locks for Spatial Indexes Shared and Exclusive Locks InnoDB implements standard row-level locking where there are two ...
https://dev.mysql.com/doc/refman/5.7/en/mysql-cluster-quick.html
To familiarize you with the basics, we describe the simplest possible configuration for a functional NDB Cluster. After this, you should be able to design your desired setup from the information provided in the other relevant sections of this ...
https://dev.mysql.com/doc/refman/5.7/en/optimizing-subqueries.html
Development is ongoing, so no optimization tip is reliable for the long term. The following list provides some interesting tricks that you might want to play with. See also Section 8.2.2, “Optimizing Subqueries, Derived Tables, and View ...
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-pre-filtering.html
Generally, the effect is to reset the summary columns to 0 or NULL, not to remove rows. Pre-filtering is done by the Performance Schema and has a global effect that applies to all users. Pre-filtering can be applied to either the producer or ...
https://dev.mysql.com/doc/refman/5.7/en/row-subqueries.html
The expression is unknown (that is, NULL) if the subquery produces no rows. Scalar or column subqueries return a single value or a column of values. A row subquery is a subquery variant that returns a single row and can thus return more than one ...
https://dev.mysql.com/doc/refman/5.7/en/bnl-bka-optimization.html
Each row from the buffer that does not have its match flag enabled is extended by NULL complements (NULL values for each column in the second operand) and sent for further extensions by the remaining join operations. In MySQL, a Batched Key Access ...
https://dev.mysql.com/doc/refman/5.7/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/5.7/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/5.7/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 ...