Data Definition Language (DDL) commands are used for defining the database structure or schema. Let's look at some DDL commands with a simple example for each command. i. CREATE In SQL, theCREATE TABLEcommand is
InSQL, different types of commands are categorized based on their functionality. These categories include Data Definition Language (DDL), Data Manipulation Language (DML), Data Control Language (DCL), and Transaction Control Language (TCL). Additionally, understanding these categories helps in effectivel...
SQL | DDL、DQL、DML、DCL 和 TCL 命令 原文:https://www . geesforgeks . org/SQL-DDL-dql-DML-DCL-TCL-commands/ 众所周知,结构化查询语言是一种数据库语言,通过它我们可以对现有的数据库执行某些操作,也可以使用这种语言来创建数据库。 SQL 使用某些命令,如创建、
UPDATE and DELETE. The changes made by DML commands are either committed or rolled back by TCL commands. There is another TCL command that can place a save point in the transactions which makes it possible to rollback all
DCL(Data Control Language)语句:即数据控制语句,用于授权/撤销数据库及其字段的权限(DCL is short name of Data Control Language which includes commands such as GRANT and mostly concerned with rights, permissions and other controls of the database system.)。常用的语句关键字有:GRANT,REVOKE。
看到很多人讨论SQL还分为四种类型,在这里知识普及一下,并总结下他们的区别吧。1. DDL – Data Definition Language数据库定义语言:定义数据库的结构。其主要命令有CREATE,ALTER,DROP等,下面用例子详解。该语言不需要commit,因此慎重。CREATE – to create objects in the database 在数据库创建对象例: CREATE DATA...
SQL(Structure Query Language)是数据库操作的的核心语言,接下来我们通过一张图来进行分析: 详细分析如下: √DDL(Data Definition Languages)语句 √DML(Data Manipulation Language)语句 &rad...数据库DDL DML DCL TCL DML(data manipulation language): 它们是SELECT、UPDATE、INSERT、DELETE,就象它的名字一样,这...
DCL DCL用于数据库控制授权,主要包括 GRANT REVOKE TCL TCL用于事务处理,主要包括 SAVEPOINT COMMIT ROLLBACK SET TRANSACTION 参考 SQL MySQL What is DDL, DML and DCL? SQL | DDL, DQL, DML, DCL and TCL Commands SQL四种语言:DDL,DML,DCL,TCL
SQL命令按照上图分为四类,DDL,DML,DCL,TCL DDL (Data Definition Language) : DDL用于定义 数据库的结构或schema,DDL也用于指定数据额外的属性。 数据存入数据库必须满足特定的一致性约束 consistency constraints 比如,假设大学要求账户余额不能为负数,DDL提供这种能力来指定这种约束。 数据库会在每次数据更新的时候来...
4. TCL – Transaction Control Language 事务控制语言 COMMIT – 保存已完成的工作 SAVEPOINT – 在事务中设置保存点,可以回滚到此处 ROLLBACK – 回滚 SET TRANSACTION – 改变事务选项 例子:Java中JDBC封装了对事务的支持。比如我们首先新建一个表:test test.sql 代码语言:javascript 代码运行次数:0 运行 AI代码...