mysql delete multi-table connection deletion function

Deleting a single table:

DELETE FROM tableName WHERE columnName = value;
Delete all rows in a table:
That is: retain the table structure, attributes, and indexes DELETE FROM tablename;
DELETE * FROM tablename;

Delete all contents in the same table (delete data, table structure)

TRUNCATE customer;

Cannot report how many rows were deleted and can only be used for a single table

Deleting multiple table connections:

DELETE orders,itrms FROM orders,items 
  WHERE orders.userid = items.userid
  AND orders.orderid = items.orderid
  AND orders.date<"2000/03/01";

The name of the table to be deleted is listed after DELETE, and the table used in the join condition is listed after FROM.

Suppose you want to delete all wine farms in the BV region, but not the place names.

DELETE winery FROM region,winery 
  WHERE winery.regionid = region.regionid
  AND region.regionname = 'BV';

The query only affects the winery table, but also uses winery and region to find the records that need to be deleted.

Using advanced join queries

DELETE orders,items FROM orders
  INNER JOIN otems ON orders.orderid = items.orderid
  AND orders.userid = items.userid
  WHERE orders.date<"2000/03/01";

You can also use nested queries (the inner query cannot reference the deleted data), GROUP BY, and HAVING in the DELETE statement;

You can also use ORDER BY in a single-table query, but it doesn't make much sense unless you use it with LIMIT to delete some data rows.

Add the quick modifier to quickly delete index items, speeding up large or frequent deletion operations.

DELETE QUICK FROM customer WHERE userid<10;

Only available for MyISAM tables.

Cleaning up MyISAM tables

OPTIMIZE TABLE customer;

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