https://dev.mysql.com/constraint-foreign-key.html
The available referential actions are RESTRICT, CASCADE, SET NULL, and NO ACTION (the default). Foreign keys let you cross-reference related data across tables, and foreign key constraints help keep this spread-out data consistent. MySQL supports ...
https://dev.mysql.com/csv-storage-engine.html
The CSV storage engine stores data in text files using comma-separated values format. The CSV storage engine is always compiled into the MySQL server. To examine the source for the CSV engine, look in the storage/csv directory of a MySQL source ...
https://dev.mysql.com/date-and-time-types.html
MySQL permits you to store a “zero” value of '0000-00-00' as a “dummy date.” In some cases, this is more convenient than using NULL values, and uses less data and index space. “Zero” date or time values used through Connector/ODBC are ...
https://dev.mysql.com/events-stages-current-table.html
END_EVENT_ID This column is set to NULL when the event starts and updated to the thread current event number when the event ends. If an event is produced from an instrument that has TIMED = NO, timing information is not collected, and TIMER_START, ...The table stores one row per thread showing the current status of the thread's most recent monitored stage event, so there is no system variable for configuring the table ...
https://dev.mysql.com/example-maximum-column-group-row.html
Task: For each article, find the dealer or dealers with the most expensive price. Other possibilities for solving the problem are to use an uncorrelated subquery in the FROM clause, a LEFT JOIN, or a common table expression with a window function.
https://dev.mysql.com/fulltext-natural-language.html
By default or with the IN NATURAL LANGUAGE MODE modifier, the MATCH() function performs a natural language search for a string against a text collection. A collection is a set of one or more columns included in a FULLTEXT index. For each row in the ...
https://dev.mysql.com/fulltext-search-mecab.html
The built-in MySQL full-text parser uses the white space between words as a delimiter to determine where words begin and end, which is a limitation when working with ideographic languages that do not use word delimiters. To address this limitation ...
https://dev.mysql.com/fulltext-search-ngram.html
The built-in MySQL full-text parser uses the white space between words as a delimiter to determine where words begin and end, which is a limitation when working with ideographic languages that do not use word delimiters. To address this limitation, ...
https://dev.mysql.com/generated-column-index-optimizations.html
row *************************** id: 1 select_type: SIMPLE table: t1 partitions: NULL type: range possible_keys: gc key: gc key_len: 5 ref: NULL rows: 1 filtered: 100.00 Extra: Using index condition In effect, the optimizer has replaced the ...For ...
https://dev.mysql.com/gis-property-functions.html
Such functions return NULL if the argument is of an incorrect geometry type. For example, the ST_Area() polygon function returns NULL if the object type is neither Polygon nor MultiPolygon. Each function that belongs to this group takes a geometry ...
