1. some words you should know:
- SQL : Structured Query Language
- DDL: Data Definition Language
- DML: Data Manipulation Language
- DCL: Data Control Language
- TPL: Transaction Processing Language
- Attribute: Attributes are the properties that define a relation.
- Tuple: Each row in the relation is known as tuple.
- Degree: The number of attributes in the relation is known as degree of the relation.
(属性列数) - Cardinality: The number of tuples in a relation is known as cardinality. (元组数)
- Column: Column represents the set of values for a particular attribute.
2. 三级模式
3. 基本概念
本文介绍了SQL语言的基础概念,包括DDL、DML、DCL、TPL等子语言,以及关系数据库中的属性、元组、度和基数等关键概念。同时,文章还探讨了数据库的三级模式体系。
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