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...
Built-in functions Built-in system objects and extensions Control-of-flow language Data definition language (DDL) statements Introduction to DDL Securing meta data objects U-SQL databases U-SQL database schemas U-SQL tables U-SQL indexes U-SQL statistics U-SQL views U-SQL functions U-SQL packa...
一、DDL 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 4.TRUNCATE - remo...
最近在项目中集成 flyway,在官方文档中有关事务处理方面,发现了一段比较有意思的一段话: If your database cleanly supports DDL statements within a transaction, failed migrations will always be rolled b…
For DDL operations that can be done in place, you can separate them into individualALTER TABLEstatements for easier scripting and maintenance, without sacrificing efficiency. For example, you might take a complicated statement such as: ALTERTABLEt1ADDINDEXi1(c1),ADDUNIQUEINDEXi2(c2),CHANGEc4_old...
大家好,我是 JiekeXu,很高兴又和大家见面了,今天和大家一起来学习利用数据泵的 SQLFILE 参数生成创建索引的 DDL 语句 数据泵功能从 10g 开始慢慢引入,从此导入导出变得更加快捷,方便。使用时只需要 help 就可以获得很多有用的参数。只要你可以登录到数据库服务器,导入导出变得更加的方便高效,可以使用命令行、参数文...
DDL是SQL语言的四大功能之一。 用于定义数据库的三级结构,包括外模式、概念模式、内模式及其相互之间的映像,定义数据的完整性、安全控制等约束 DDL不需要commit. CREATE ALTER DROP TRUNCATE COMMENT RENAME 2.DML(Data Manipulation Language)数据操纵语言statements are used for managing data within schema objects. ...
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...
The number of SQL DROP ALIAS statements executed. Field Name:QXDRPAL DROP PACKAGE The number of SQL DROP PACKAGE statements executed. Field Name:QXDRPPKG DROP DISTINCT TYPE The number of DROP DISTINCT TYPE statements executed. Field Name:QXDDIST ...
Compound Statements Contents Data Definition Data Manipulation Data Types Functions Geographic Features Help Metadata Language Structure Plugins Procedures Storage Engines Table Maintenance Transactions User-Defined Functions Utility mysql> help Functions; 查询这个模块下有哪些信息 ...