https://dev.mysql.com/statement-histogram-summary-tables.html
The statement histogram summary tables have these indexes: events_statements_histogram_by_digest: Unique index on (SCHEMA_NAME, DIGEST, BUCKET_NUMBER) events_statements_histogram_global: Primary key on (BUCKET_NUMBER) TRUNCATE TABLE is permitted for ... The Performance Schema maintains statement event summary tables that contain information about minimum, maximum, and average statement latency (see Section 26.12.17.3, “Statement Summary ...
https://dev.mysql.com/statistics-table.html
NON_UNIQUE 0 if the index cannot contain duplicates, 1 if it can. CARDINALITY An estimate of the number of unique values in the index. The information_schema_stats_expiry system variable defines the period of time before cached table statistics ...
https://dev.mysql.com/subquery-materialization.html
The index contains unique values to eliminate duplicates and make the table smaller. The optimizer uses materialization to enable more efficient subquery processing. Materialization speeds up query execution by generating a subquery result as a ...
https://dev.mysql.com/table-cache.html
Also take into account that the MyISAM storage engine needs two file descriptors for each unique open table. When you execute a mysqladmin status command, you should see something like this: Uptime: 426 Running threads: 1 Questions: 11082 Reloads: ...
https://dev.mysql.com/trigger-syntax.html
Trigger names exist in the schema namespace, meaning that all triggers must have unique names within a schema. To create a trigger or drop a trigger, use the CREATE TRIGGER or DROP TRIGGER statement, described in Section 13.1.22, “CREATE TRIGGER ...
https://dev.mysql.com/wait-summary-tables.html
If an instrument is used to create multiple instances, each instance has a unique OBJECT_INSTANCE_BEGIN value and is summarized separately in this table. The Performance Schema maintains tables for collecting current and recent wait events, and ...
https://dev.mysql.com/what-is-mysql.html
You set up rules governing the relationships between different data fields, such as one-to-one, one-to-many, unique, required or optional, and “pointers” between different tables. MySQL, the most popular Open Source SQL database management ...
https://dev.mysql.com/where-optimization.html
A table that is used with a WHERE clause on a PRIMARY KEY or a UNIQUE index, where all index parts are compared to constant expressions and are defined as NOT NULL. This section discusses optimizations that can be made for processing WHERE clauses.
