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https://dev.mysql.com/doc/refman/8.0/en/innodb-online-ddl-operations.html
The rows of an InnoDB table are stored in a clustered index organized based on the primary key, forming what some database systems call an “index-organized table”. Dropping a column default value ALTER TABLE tbl ALTER COLUMN col DROP DEFAULT, ...
https://dev.mysql.com/doc/refman/8.0/en/mysql-commands.html
This behavior on the server side comes into play for multiple-statement execution (see Multiple Statement Execution Support), and for parsing the body of stored procedures and functions, triggers, and events (see Section 27.1, “Defining Stored ...
https://dev.mysql.com/doc/refman/8.0/en/performance-schema-statement-summary-tables.html
Each row summarizes events for a given stored program (stored procedure or function, trigger, or event). The events_statements_summary_by_program table has these additional summary columns: COUNT_STATEMENTS, SUM_STATEMENTS_WAIT, MIN_STATEMENTS_WAIT, ... The Performance Schema maintains tables for collecting current and recent statement events, and aggregates that information in summary ...
https://dev.mysql.com/doc/refman/8.0/en/char.html
The CHAR and VARCHAR types are similar, but differ in the way they are stored and retrieved. The CHAR and VARCHAR types are declared with a length that indicates the maximum number of characters you want to store. When CHAR values are stored, they ...They also differ in maximum length and in whether trailing spaces are ...
https://dev.mysql.com/doc/refman/8.0/en/string-type-syntax.html
[NATIONAL] CHAR[(M)] [CHARACTER SET charset_name] [COLLATE collation_name] A fixed-length string that is always right-padded with spaces to the specified length when stored. MySQL stores VARCHAR values as a 1-byte or 2-byte length prefix plus data.
https://dev.mysql.com/doc/refman/8.0/en/select-into.html
For the INTO var_list variant: var_list names a list of one or more variables, each of which can be a user-defined variable, stored procedure or function parameter, or stored program local variable. INTO form of SELECT enables a query result to be ...Column and line terminators can be specified to produce a specific output ...
https://dev.mysql.com/doc/refman/8.0/en/time-zone-support.html
This includes the values displayed by functions such as NOW() or CURTIME(), and values stored in and retrieved from TIMESTAMP columns. Nor are values in those data types stored in UTC; the time zone applies for them only when converting from ...
https://dev.mysql.com/doc/refman/8.0/en/diagnostics-area.html
The following example shows the effect of various statements on the diagnostics area, using SHOW WARNINGS to display information about conditions stored there. Diagnostics areas are pushed to and popped from the stack under the following ... SQL ...
https://dev.mysql.com/doc/refman/8.0/en/exists-and-not-exists-subqueries.html
If a subquery returns any rows at all, EXISTS subquery is TRUE, and NOT EXISTS subquery is FALSE. For example: SELECT column1 FROM t1 WHERE EXISTS (SELECT * FROM t2); Traditionally, an EXISTS subquery starts with SELECT *, but it could begin with ...
https://dev.mysql.com/doc/refman/8.0/en/innodb-compression-internals.html
InnoDB Data Storage and Compression All user data in InnoDB tables is stored in pages comprising a B-tree index (the clustered index). The compression of B-tree nodes (of both clustered and secondary indexes) is handled differently from compression ... This section describes some internal implementation details about compression for InnoDB ...