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https://dev.mysql.com/doc/refman/8.4/en/create-table-check-constraints.html
expr specifies the constraint condition as a boolean expression that must evaluate to TRUE or UNKNOWN (for NULL values) for each row of the table. CREATE TABLE permits the core features of table and column CHECK constraints, for all storage engines. CREATE TABLE permits the following CHECK constraint syntax, for both table constraints and column constraints: [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED] The optional symbol specifies a name for the ...
https://dev.mysql.com/doc/refman/8.4/en/data-masking-component-usage.html
Thus, even though ssn is defined as VARCHAR(11), if the ssn column has a multibyte character set, it may appear to be longer than 11 bytes when passed to a loadable function, and returns NULL while logging the error. Before using MySQL Enterprise ...
https://dev.mysql.com/doc/refman/8.4/en/data-size.html
It makes SQL operations faster, by enabling better use of indexes and eliminating overhead for testing whether each value is NULL. If you really need NULL values in your tables, use them. Just avoid the default setting that allows NULL values in ...
https://dev.mysql.com/doc/refman/8.4/en/date-and-time-literals.html
Standard SQL and ODBC Date and Time Literals String and Numeric Literals in Date and Time Context Date and time values can be represented in several formats, such as quoted strings or as numbers, depending on the exact type of the value and other ...
https://dev.mysql.com/doc/refman/8.4/en/events-configuration.html
row *************************** Id: 1 User: root Host: localhost db: NULL Command: Query Time: 0 State: NULL Info: show processlist *************************** 2. row *************************** Id: 2 User: event_scheduler Host: localhost db: NULL ... Events are executed by a special event scheduler thread; when we refer to the Event Scheduler, we actually refer to this ...
https://dev.mysql.com/doc/refman/8.4/en/explain-extended.html
row *************************** id: 1 select_type: PRIMARY table: t1 type: index possible_keys: NULL key: PRIMARY key_len: 4 ref: NULL rows: 4 filtered: 100.00 Extra: Using index *************************** 2. row *************************** id: 2 ... The EXPLAIN statement produces extra (“extended”) information that is not part of EXPLAIN output but can be viewed by issuing a SHOW WARNINGS statement following ...
https://dev.mysql.com/doc/refman/8.4/en/gis-polygon-property-functions.html
Unless otherwise specified, functions in this section handle their geometry arguments as follows: If any argument is NULL or any geometry argument is an empty geometry, the return value is NULL. ST_Centroid() handles its arguments as described in ...
https://dev.mysql.com/doc/refman/8.4/en/gis-wkb-functions.html
Unless otherwise specified, functions in this section handle their geometry arguments as follows: If the WKB or SRID argument is NULL, the return value is NULL. If the options argument is NULL, the return value is NULL. These functions take as ...
https://dev.mysql.com/doc/refman/8.4/en/group-by-handling.html
The query is invalid if name is not a primary key of t or a unique NOT NULL column. SQL-92 and earlier does not permit queries for which the select list, HAVING condition, or ORDER BY list refer to nonaggregated columns that are not named in the ...
https://dev.mysql.com/doc/refman/8.4/en/help.html
If X is less than or equal to 0.0E0, the function returns NULL and a warning "Invalid argument for logarithm" is reported. URL: https://dev.mysql.com/doc/refman/8.4/en/mathematical-functions.html Examples: mysql> SELECT LOG(2); -> 0.69314718055995 ... HELP 'search_string' The HELP statement returns online information from the MySQL Reference ...