https://dev.mysql.com/sys-user-summary-by-statement-latency.html
Rows for which the USER column in the underlying Performance Schema table is NULL are assumed to be for background threads and are reported with a host name of background. The user_summary_by_statement_latency and x$user_summary_by_statement_latency ...
https://dev.mysql.com/sys-user-summary-by-statement-type.html
Rows for which the USER column in the underlying Performance Schema table is NULL are assumed to be for background threads and are reported with a host name of background. These views summarize informaion about statements executed, grouped by user ...
https://dev.mysql.com/sys-user-summary.html
Rows for which the USER column in the underlying Performance Schema table is NULL are assumed to be for background threads and are reported with a host name of background. These views summarize statement activity, file I/O, and connections, grouped ...
https://dev.mysql.com/tp-thread-state-table.html
Note The Performance Schema table described here is available as of MySQL 8.0.14. Prior to MySQL 8.0.14, use the corresponding INFORMATION_SCHEMA table instead; see Section 25.47.3, “The INFORMATION_SCHEMA TP_THREAD_STATE Table”. The ...
https://dev.mysql.com/truncate-table.html
TRUNCATE TABLE can be used with Performance Schema summary tables, but the effect is to reset the summary columns to 0 or NULL, not to remove rows. Logically, TRUNCATE TABLE is similar to a DELETE statement that deletes all rows, or a sequence of ...
https://dev.mysql.com/udf-features.html
You can indicate that a function returns NULL or that an error occurred. The MySQL interface for user-defined functions provides the following features and capabilities: Functions can return string, integer, or real values and can accept arguments ...
https://dev.mysql.com/users-table.html
This is NULL for an internal thread, or for a user session that failed to authenticate. The users table contains a row for each user who has connected to the MySQL server. For each user name, the table counts the current and total number of ...
https://dev.mysql.com/values.html
VALUES is a DML statement introduced in MySQL 8.0.19 which returns a set of one or more rows as a table. In other words, it is a table value constructor which also functions as a standalone SQL statement. VALUES row_constructor_list [ORDER BY ...
https://dev.mysql.com/wait-summary-tables.html
This value is calculated only for timed events because nontimed events have a wait time of NULL. The Performance Schema maintains tables for collecting current and recent wait events, and aggregates that information in summary tables. Section ...
https://dev.mysql.com/window-functions-usage.html
NULL values sort first for ascending sorts, last for descending sorts. However, whereas an aggregate operation groups query rows into a single result row, a window function produces a result for each query row: The row for which function evaluation ...
