Бази даних

Реляційні бази даних (цілісність даних)

Сутності зберігаються в таблицях

Course

Колонки – атрибути сутностей

Name, Description, StartData, EndDate, ApplicationEndDate

Рядки – екземпляри сутностей

Визначаються лише атрибутами (не порядковим номером)

Найчастіше рядки є унікальними

Edgar Codd

Primary key визначає унікальність рядка.

Один або декілька атрибутів (Name + Description; Id)

Для зміни структури та отримання/редагування даних використовується мова SQL

Data Manipulation Language – DML

Data Definition Language – DDL

SQL Server http://msdn.microsoft.com/en-us/library/bb510741.aspx

SQL Server 2012 Express LocalDB

http://msdn.microsoft.com/en-us/library/hh510202.aspx

No full server instance of SQL Server.

SqlLocalDB.exe

Create database

create database LectureExample

drop database LectureExample

Create table

create table Course(

Id int identity primary key,Name nvarchar(255),[Description] nvarchar(max),StartDate datetime2,EndDate datetime2,ApplicationEndDate datetime2

);

Data typesData types http://msdn.microsoft.com/en-us/library/ms187752.aspx

bigint, numeric, bit, smallint, decimal, smallmoney, int, tinyint, money

float, real

date, datetimeoffset, datetime2, smalldatetime, datetime, time

char, varchar, text

nchar, nvarchar, ntext

Insert, select, delete

insert into Course (Name, [Description], StartDate) values(N'C++ Feb 2013', N'...', '1/31/2013'),(N'C# 2012', N'...', '3/19/2013')

select * from Course

select Name, StartDate, EndDatefrom Course

delete Course

Завжди вказуйте перелік колонок

Не використовуйте ‘select *’ в коді

Order by

select Name, StartDate from Courseorder by StartDate asc

select Name, StartDate from Coursewhere enddate is nullorder by StartDate desc

select top(2) Name, StartDate from Coursewhere enddate is nullorder by StartDate desc

Pagingselect Name, StartDate from Courseorder by StartDate desc

offset 1 rowsfetch next 3 rows only

All rows

Page of size 3 starting from 2nd row

Aggregationsselect count(*) from Coursewhere EndDate is null

select sum(Id) from Course

select Id, Name, TeacherName,TeacherYearsOfExperiencefrom Course

A Teacher teaches a Course

Дані дублюються

Вирішення – окрема таблиця для Teacher

create table Teacher(

Id int identity primary key,Name nvarchar(255),YearsOfExperience int

)

Teacher

Course

Foreign keycreate table Course(

Id int identity primary key,Name nvarchar(255),TeacherId int,

constraint FK_Course_Teacherforeign key (TeacherId)references Teacher(Id)

);

Inner joinselect Course.Id, Course.Name, Teacher.Id,

Teacher.Namefrom Courseinner join Teacher

on Course.TeacherId = Teacher.Id

Left outer joinselect Course.Id, Course.Name, Teacher.Id,

Teacher.Namefrom Courseleft join Teacher

on Course.TeacherId = Teacher.Id

Right outer joinselect Course.Id, Course.Name, Teacher.Id,

Teacher.Namefrom Courseright join Teacher

on Course.TeacherId = Teacher.Id

“Right join” via left joinselect Course.Id, Course.Name, Teacher.Id,

Teacher.Namefrom Teacherleft join Course

on Course.TeacherId = Teacher.Id

Full outer joinselect Course.Id, Course.Name, Teacher.Id,

Teacher.Namefrom Coursefull outer join Teacher

on Course.TeacherId = Teacher.Id

Update

update Teacher set YearsOfExperience = 13where Id = 1

update Teacher set

YearsOfExperience = 15,Name = 'Walter White Junior'

where Id = 1

Delete

delete Teacher where Id = 4