sql-基础-概念

　　Sql语言的概念包含3部分内容。sql的历史，以及各个版本的历史，Sql标准的组成部分，Sql语句的分类。

1、版本

　　SQL-87：Standard first formalized by ANSI; support for transactions and CREATE, READ, UPDATE, and DELETE operations

    　标准的新增，查询，更新，删除操作。

    　SQL-89：Minor revision, added referential integrity constraints

    　完整性约束。

       SQL-92：Major revision (ISO 9075), added support for internationalization, etc.

    　增加国际化。

    　SQL-1999：Added support for user-defined types, regular expression mapping, triggers, procedural and control-flow statements, and more

    　增加用户自定义类型，正则表达式，触发器，procedural和流程控制语句等。

    　SQL-2003：Added support for XML and OLAP (window functions), sampling, and enhanced numeric functions

    　支持XML和OLAP, 增强数字函数

    　SQL-2006：Clarified how SQL and SML interact and added support for XQuery

    　支持Xquery

    　SQL-2008：Incorporated various improvements and enhancements that had been made in several of the most prominent RDBMS platforms (INSTEAD OF triggers, TRUNCATE statement, FETCH clause, etc.) and expanded the XML specification

    　对原有的一些对象进行增强

　　SQL-2011: Introduced new features for managing temporal data

　　管理临时数据增加新功能。

　　SQL-2016：Described how SQL interacts with JavaScript Object Notation (JSON) and added support for polymorphic table functions and row pattern matching

　　增加Json的支持。

    　SQL-2019：Described how SQL interacts with multidimensional arrays (MDAs)

　　增加多维数组。

2、组成部分

 　　SQL/Framework：

　　SQL/Foundation：

　　SQL/CLI (Call-Level Interface)：从其他编程语言动态执行sql

　　SQL/PSM (Persistent Stored Modules)

　　SQL/MED (Management of External Data)

　　SQL/OLB (Object Language Binding)：与面向对象语言绑定，例如JDBC

　　SQL/Schemata：元信息

　　SQL/JRT (Java Routines and Types)：

　　SQL/XML：添加XML数据类型，并实现相关的操作。

3、语句分类