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https://dev.mysql.com/doc/refman/5.7/en/examples.html
Some of the examples use the table shop to hold the price of each article (item number) for certain traders (dealers). Here are examples of how to solve some common problems with MySQL. Supposing that each trader has a single fixed price per ...
https://dev.mysql.com/doc/refman/5.7/en/fetching-spatial-data.html
Geometry values stored in a table can be fetched in internal format. Fetching spatial data in internal format: Fetching geometry values using internal format can be useful in table-to-table transfers: CREATE TABLE geom2 (g GEOMETRY) SELECT g FROM ...SELECT ST_AsText(g) FROM geom; Fetching spatial data in WKB format: The ST_AsBinary() function converts a geometry from internal format to a BLOB containing the WKB ...
https://dev.mysql.com/doc/refman/5.7/en/fractional-seconds.html
For example: CREATE TABLE t1 (t TIME(3), dt DATETIME(6)); The fsp value, if given, must be in the range 0 to 6. MySQL has fractional seconds support for TIME, DATETIME, and TIMESTAMP values, with up to microseconds (6 digits) precision: To define a ...
https://dev.mysql.com/doc/refman/5.7/en/group-by-functional-dependence.html
The following discussion provides several examples of the ways in which MySQL detects functional dependencies. The examples use this notation: {X} -> {Y} Understand this as “X uniquely determines Y,” which also means that Y is functionally ...
https://dev.mysql.com/doc/refman/5.7/en/group-replication-monitoring.html
These Performance Schema tables display information specific to Group Replication: replication_group_member_stats: See Section 17.4.3, “The replication_group_member_stats Table”. These Performance Schema replication tables also show information ... You can use the MySQL Performance Schema to monitor Group ...
https://dev.mysql.com/doc/refman/5.7/en/index-btree-hash.html
One circumstance under which this occurs is when the optimizer estimates that using the index would require MySQL to access a very large percentage of the rows in the table. (In this case, a table scan is likely to be much faster because it requires ... Understanding the B-tree and hash data structures can help predict how different queries perform on different storage engines that use these data structures in their indexes, particularly for the MEMORY storage engine that lets you choose B-tree or hash ...
https://dev.mysql.com/doc/refman/5.7/en/innochecksum.html
This tool reads an InnoDB tablespace file, calculates the checksum for each page, compares the calculated checksum to the stored checksum, and reports mismatches, which indicate damaged pages. It was originally developed to speed up verifying the ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-data-dictionary.html
The InnoDB data dictionary is comprised of internal system tables that contain metadata used to keep track of objects such as tables, indexes, and table columns. For historical reasons, data dictionary metadata overlaps to some degree with ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-deadlock-detection.html
InnoDB is aware of table locks if innodb_table_locks = 1 (the default) and autocommit = 0, and the MySQL layer above it knows about row-level locks. Otherwise, InnoDB cannot detect deadlocks where a table lock set by a MySQL LOCK TABLES statement or ... When deadlock detection is enabled (the default), InnoDB automatically detects transaction deadlocks and rolls back a transaction or transactions to break the ...
https://dev.mysql.com/doc/refman/5.7/en/innodb-disk-management.html
This section discusses the main considerations for I/O and disk space with the default kind of MySQL tables (also known as InnoDB tables): Controlling the amount of background I/O used to improve query performance. Organizing tables into many small ... As a DBA, you must manage disk I/O to keep the I/O subsystem from becoming saturated, and manage disk space to avoid filling up storage ...