DROP TABLE IF EXISTS course --创建course表 CREATE TABLE course(cid VARCHAR(10),cname VARCHAR(10),teid VARCHAR(10)); --初始化数据 INSERT INTO course VALUES('01' , '语文' , '02'); INSERT INTO course VALUES('02' , '数学' , '01'); INSERT INTO course VALUES('03' , '英语' , '0...
The delete statement is used in SQL to delete the current records in the table. Whenever the requirement arises, and we do not want certain records, the delete statement is used along with the Where clause to remove those records. The syntax for the same is as below: DELETE FROM table_na...
1要从数据库中删除一个表,应该使用的SQL语句是( )。 A.ALTER TABLE B.KILL TABLEC.DELETE TABLE D.DROP TABLE 2要从数据库中删除―个表,应该使用的SQI语句是___。 A.ALTER TABLEB.KILL TABLEC.DELETE TABLED.DROP TABLE 3要从数据库中删除一个表,应该使 用的SQL语句是( ) A. ALTER TABLE B. ...
库与表 Table aliases 关于表别名,相信大家都不陌生;指定表别名是为了简化SQL,使可读性更强 语法如下 AS可以省略 应用到tbl_user上则是 不仅表可以指定别名,列也可以指定别名,这里就不展开了 DELETE 对于DELETE,相信大家已经非常熟悉了 单表语法如下 多表语法如下 DELETE + Table aliases SELECT的时候,我们经常用...
以下示例演示DROP命令的使用,依次执行如下SQL语句: --删除整个表course DROP TABLE IF EXISTS course --创建course表 CREATE TABLE course(cid VARCHAR(10),cname VARCHAR(10),teid VARCHAR(10));--初始化数据 INSERT INTO course VALUES('01','语文','02');INSERT INTO course VALUES('02','数学','01')...
SQL DELETESales.ShoppingCartItemOUTPUTDELETED.*WHEREShoppingCartID =20621;--Verify the rows in the table matching the WHERE clause have been deleted.SELECTCOUNT(*)AS[RowsinTable]FROMSales.ShoppingCartItemWHEREShoppingCartID =20621; GO J. 在 DELETE 语句中同时使用 OUTPUT 与 <from_table_name> ...
The DELETE statement in SQL can delete multiple rows by specifying a condition that matches more than one row. Example: CREATE TABLE orders (order_id INT PRIMARY KEY,customer_id INT,status VARCHAR(50));INSERT INTO orders (order_id, customer_id, status) VALUES(101, 1, 'Pending'),(102, ...
对于查询情况,其实MySQL提供给我们一个功能来引导优化器更好的优化,那便是MySQL的查询优化提示(Query Optimizer Hints)。比如,想让SQL强制走索引的话,可以使用 FORCE INDEX 或者USE INDEX;它们基本相同,不同点:在于就算索引的实际用处不大,FORCE INDEX也得要使用索引。
for_delete; Query OK, 3 rows affected (0.04 sec) mysql> insert for_delete (name) values ('D'); Query OK, 1 row affected (0.02 sec) mysql> select * from for_delete; +---+---+ | id | name | +---+---+ | 4 | D | +---+---+ 1 row in set (0.00 sec)截断表 trunca...
在系统表上不能使用DROP TABLE语句。如果删除表内的所有行(DELETE tablename)或使用TRUNCATE TABLE语句,则表将一直存在到被除去。2、DELETE删除所有行;可以在不删除表的情况下删除所有的行。这意味着表的结构、属性和索引都是完整的:DELETE FROM table_name或者:DELETE * FROM table_name。区别四、使用用法不同1...