Chapter 7

SQLHUANG XUEHUA

SQL

SQL server2005 introduction

Install components

management studio

SQL Data Definition Basic Query Structure Set Operations Aggregate Functions Null Values Nested Subqueries Complex Queries Views Modification of the Database Joined Relations**

History

IBM Sequel language developed as part of System R project at the IBM San Jose Research Laboratory

Renamed Structured Query Language (SQL) ANSI and ISO standard SQL:

SQL-86 SQL-89 SQL-92 SQL:1999 SQL:2003

Not all examples here may work on your particular system.

Sub-languages of SQL

The Data Definition Language (DDL) is a computer language for defining data structures. The DDL group is made up of theses statements: CREATE causes an object (a table, for example) to be created within

the database. ALTER statement permits the user to modify an existing object in

various ways -- for example, adding a column to an existing table. RENAME causes a table’s name to be changed TRUNCATE deletes all data from a table (non-standard, but common

SQL statement). DROP causes an existing object within the database to be deleted,

usually irretrievably.

Sub-languages of SQL

SQL is made up of three major sub-languages, which are Data Definition Language (DDL), Data Manipulation Language (DML), and Data Control Language (DCL). The Data Manipulation Language (DML) is a computer language used to

retrieve or modify the content of tables within the database. The DML group is made up of theses statements: SELECT is used to retrieve or display tuples from the table(s) that satisfy a

given condition. INSERT is used to add tuples (rows) to an existing table UPDATE is used to modify the values of a set of existing table rows. DELETE removes zero or more existing rows from a table All the members in this group modifies the content of the table except the

Select statement, which only display the content of the table(s).

Sub-languages of SQL

The Data Control Language (DCL) is a computer language and a subset of SQL, used to control access to data in a database. The DCL group is made up of theses statements: GRANT to allow specified users to perform specified tasks REVOKE to cancel previously granted or denied permissions Some of the following things or privileges that can be GRANTED TO or

REVOKED FROM a user or role are CONNECT, SELECT, INSERT, UPDATE, DELETE, and USAGE.

Data Definition, Constraints, and Schema Changes

Used to CREATE, DROP, and ALTER the descriptions of the tables (relations) of a database

Syntax: CREATE DATABASE database_name ; CREATE TABLE table_name (

column_name1 data_type constraint,

column_name2 data_type, ....... )

数据类型 符号标识 数据类型 符号标识整数型 bigint 、 int 、 smallint 、

tinyint精确数值型 decimal 、 numeric

浮点型 float 、 real 货币型 money 、 smallmoney

位型 bit 字符型 char 、 varchar

Unicode 字符型

nchar 、 nvarchar 文本型 text 、 ntext

二进制型 binary 、 varbinary 日期时间类型 datetime 、 smalldatetime

时间戳型 timestamp 图像型 image

其他 cursor 、 sql_variant 、 table 、 uniqueidentifier

Data type

Domain Types in SQL

char(n). Fixed length character string, with user-specified length n. varchar(n). Variable length character strings, with user-specified maximu

m length n. int. Integer (a finite subset of the integers that is machine-dependent). smallint. Small integer (a machine-dependent subset of the integer domai

n type). numeric(p,d). Fixed point number, with user-specified precision of p digi

ts, with d digits to the right of decimal point. real, double precision. Floating point and double-precision floating point

numbers, with machine-dependent precision. decimal(n,s). Floating point number, with user-specified precision of at le

ast n digits.

Integrity Constraints on Tables

not null primary key (A1, ..., An )

Example: Declare branch_name as the primary key for branch. create table branch

(branch_name char(15), branch_city char(30) not null, assets integer, primary key (branch_name))

Drop and Alter Table Constructs

The drop table command deletes all information about the dropped relation from the database.

The alter table command is used to add attributes to an existing relation:

alter table r add A D

where A is the name of the attribute to be added to relation r and D is the domain of A.

All tuples in the relation are assigned null as the value for the new

attribute. The alter table command can also be used to drop attributes of a relation:

alter table r drop A

where A is the name of an attribute of relation r Dropping of attributes not supported by many databases

Summary

From this lecture you can learn the basic syntax of data definition language.

Create table Primary key Unique Not null Default Foreign key

Any Questions?If there are any outstanding questions you can ask me one-to-one after the lecture OR privately in my office.

Exercises

Create the company schema on the machine