DDL is Data Definition Language statements. Some examples:数据定义语言,用于定义和管理SQL数据库中的所有对象的语言 1.CREATE - to create objects in the database 创建 2.ALTER - alters the structure of the database 修改 3.DROP - delete
SQL是一个标准的数据库语言,是面向集合的描述性非过程化语言。它功能强,效率高,简单易学易维护。然而SQL语言由于以上优点,同时也出现了这样一个问题: 它是非过程性语言,即大多数语句都是独立执行的,与上下文无关,而绝大部分应用都是一个完整的过程,显然用SQL完全实现这些功能是很困难的。
DML (Data Manipulation Language) are SQL commands focused on handling data within the database, including most SQL statements. Let's look at some DML commands with a simple example for each command. i. INSERT INTO In SQL, theINSERT INTOstatement is used to insert new rows into a database ...
Explain可以用来迅速方便地查出对于给定SQL语句中的查询数据是如何得到的即搜索路径(我们通常称为Access Path)。从而使我们选择最优的查询方式达到最大的优化效果。 LOCK TABLE- control concurrency 锁,用于控制并发 三、DCL is Data Control Language statements. Some examples:数据控制语言,用来授予或回收访问数据库的...
一、DDL is Data Definition Language statements 数据定义语言,用于定义和管理 SQL 数据库中的所有对象的语言 1.CREATE - to create objects in the database 创建 2.ALTER - alters the structure of the database 修改 3.DROP - delete objects from the database 删除 ...
DDLis Data Definition Language statements. Some examples:数据定义语言,用于定义和管理 SQL 数据库中的所有对象的语言 1.CREATE - to create objects in the database 创建 2.ALTER - alters the structure of the database 修改 3.DROP - delete objects from...
CALL - call a PL/SQL or Java subprogram EXPLAIN PLAN - explain access path to data LOCK TABLE - control concurrency DCL Data Control Language (DCL) statements. Some examples: GRANT - gives user's access privileges to database REVOKE - withdraw access privileges given with the GRANT command ...
SQL_DDL_DML_DCL的介绍 DDL is Data Definition Language statements. Some examples:数据定义语言,用于定义和管理 SQL 数据库中的所有对象的语言 1.CREATE - to create objects in the database 创建 2.ALTER - alters the structure of the database 修改...
DDL is Data Definition Language statements. Some examples:数据定义语言,用于定义和管理 SQL 数据库中的所有对象的语言 1.CREATE - to create objects in the database 创建 2.ALTER - alters the structure of the database 修改 3.DROP - delete objects from the database 删除 ...
CREATE Command:The database or its objects are created with this command (like table, index, function, views, store procedure, and triggers). There are two types of CREATE statements in SQL, one is for the creation of a database and the other for a table. ...