SQL 复制 USE AdventureWorks2022; GO ALTER TABLE dbo.DocExe DROP CONSTRAINT FK_Column_B; GO 有关详细信息,请参阅 ALTER TABLE (Transact-SQL)。 后续步骤 ALTER TABLE (Transact-SQL) sys.key_constraints (Transact-SQL) 创建外键关系 修改外键关系反馈...
-- Syntax for SQL Server and Azure SQL Database[WITH<common_table_expression>[ ,...n ] ]DELETE[TOP( expression ) [PERCENT] ] [FROM] { {table_alias|<object>|rowset_function_limited[WITH(table_hint_limited[ ...n ] ) ] } | @table_variable} [<OUTPUT Clause>] [FROMtable_source[ ...
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO ALTER TABLE [dbo].[Car] WITH CHECK ADD CONSTRAINT [FK_Car_People] FOREIGN KEY([PeopleID]) REFERENCES [dbo].[People] ([ID]...
数据查询语言(DQL,Data Query Language):基本结构是由SELECT子句,FROM子句,WHERE子句组成的查询块。 数据操纵语言(DML,Data Manipulation Language):是SQL语言中,负责对数据库对象运行数据访问工作的指令集,以INSERT、UPDATE、DELETE三种指令为核心,分别代表插入、更新与删除,是开发以数据为中心的应用程序必定会使用到的指...
CONSTRAINT OrdersPK PRIMARY KEY (order_id), FOREIGN KEY (customer_id) REFERENCES Customers(id) ); Here, the value of thecustomer_idcolumn in theOrderstable references the row in another table namedCustomerswith itsidcolumn. Note:The above code works in all major database systems. However, th...
DELETE FROM table_name WHERE primary_key=value; INSERT INTO table_name VALUES (...); 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 4. 外键约束错误 典型错误: 复制下载 ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails ...
Method 1: Deleting a Single Row in SQL The DELETE statement in SQL uses the WHERE clause to specifically delete a record from the table. Example: CREATE TABLE customers (customer_id INT PRIMARY KEY,name VARCHAR(50),city VARCHAR(50),email VARCHAR(100));INSERT INTO customers (customer_id, ...
WITH ROLLUP:将会在所有记录的最后加上一条记录。加上的这一条记录是上面所有记录的总和。 mysql>SELECT sex,COUNT(sex) FROM employee GROUP BY sexWITH ROLLUP; +---+---+ | sex | COUNT(sex) | +---+---+ |女 | 2 | |男 | 3 | | NULL...
语法：UPDATE table_name SET 字段名='新值' [, 字段2='新值', …] [WHERE 条件语句];删除数据：删除整个表中的数据：DELETE FROM table_name;删除表中指定条件的数据：DELETE FROM table_name WHERE 条件语句;创建数据库用户：语法：CREATE USER username1 IDENTIFIED BY 'password', username2 ...
delete from tb1; #清空表内容 truncate table tb1; #清空表内容 select * from tb1; #查看表中所有数据 数据表基本操作 1、创建表 1 2 3 4 create table 表名( 列名 类型 是否可以为空, 列名 类型 是否可以为空 )ENGINE=InnoDB DEFAULT CHARSET=utf8 ...