DELETE FROM tableName WHERE columnName = value;
删除表内的所有行：
即：保留表的结构、属性、索引
DELETE FROM tablename;
DELETE * FROM tablename;

TRUNCATE customer;

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

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

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

DELETE QUICK FROM customer WHERE userid<10;

OPTIMIZE TABLE customer;