The goal is to delete a specific employee record from the Employees table. This demonstrates how to use the DELETE statement to remove a single row from a table based on a condition. 2. Key Components : DELETE
DELETEFROMtable_nameWHEREcondition; Note:Be careful when deleting records in a table! Notice theWHEREclause in theDELETEstatement. TheWHEREclause specifies which record(s) should be deleted. If you omit theWHEREclause, all records in the table will be deleted!
-- 从数据库中删除数据 DELETE FROM table_name [ WHERE <condition> ]; 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 TRUNCATE TABLE -- 清空表 TRUNCATE TABLE table_name; TRUNCATE TABLE 和 DROP TABLE TRUN...
删除记录:record = session.query(MyTable).filter_by(id=record_id).first() session.delete(record) session.commit()请将MyTable替换为实际的映射类名,record_id替换为要删除的记录的ID。 以上代码会从数据库中查询出指定ID的记录,并将其删除。最后需要调用session.commit()方法提交事务,使删除操作生效。 SQL...
DELETE SQL Command Marks records as deleted. It's similar toDelete Record from DBF filecommand fromEditmenu. You can restore those records by using theRecall Recordcommand. Records marked as deleted physically removes from theDBFfile when the PACK command is executed. See it's description below...
create table b ( id int identity(1,1) primary key, name varchar(50) not null, userId varchar(20), foreign key (userId) references a(id) on delete cascade ) 表B创建了外码userId 对应A的主码ID,声明了级联删除 测试数据: insert a values (’11’,’aaa’) insert a values(’23’,’...
The SQL DELETE StatementThe DELETE statement is used to delete rows in a table.SQL DELETE SyntaxDELETE FROM table_name WHERE some_column=some_value; Notice the WHERE clause in the SQL DELETE statement! The WHERE clause specifies which record or records that should be deleted. If you omit ...
DELETEFROMtableWHEREcondition 删除前可以验证一下: Copy SELECTCOUNT(*)FROMtableWHEREcondition 如果想要删除所有的行,可以: Copy DELETEFROMtable 或者 Copy TRUNCATETABLEtable TRUNCATE TABLE优势在于速度更快,但是不提供记录事务的结果。 另外一个不同点是,TRUNCATE TABLE重新设置了用于自增型的列的当前值,DELETE不...
DELETE FROM Customers WHERE CustomerName='Alfreds Futterkiste'; Try it Yourself » Note: Be careful when deleting records in a table! Notice the WHERE clause in the DELETE statement. The WHERE clause specifies which record(s) should be deleted. If you omit the WHERE clause, all records ...
行(ROW):表中的数据是按行存储,每个记录存储在自己的行内,也可以称作数据库记录(RECORD); 主键(PRIMARY KEY):表的一个字段(即一列),用来唯一标识表中的每一行;主键必不可少; 充当主键的条件: 1.任意两行不能具有相同的主键值; 2.每一行都必须具有一个主键值(且不能为NULL); ...