. Net0809 notes

The time has passed so fast that the basic enhanced course has been completed and the database course has now started. Database creation: createdatabaseMySchoolonprimary (nameMySchool, fileNameD: ProgramFilesMicrosoftSQLServerMSSQL10.MSSQLSERVERMSSQLDATAMySchool. mdf, size10MB,

The time has passed so fast that the basic enhanced course has been completed and the database course has now started. Database creation: create database MySchool on primary (name = 'myschool ', fileName = 'd: \ Program Files \ Microsoft SQL Server \ MSSQL10.MSSQLSERVER \ MSSQL \ DATA \ MySchool. mdf ', size = 10 MB,

The time passed so fast that the basic Enhancement Course has ended. The Hong Kong server has now started the database course.

Database creation:

Create database MySchool
On primary
(
Name = 'myschool ',
FileName = 'd: \ Program Files \ Microsoft SQL Server \ MSSQL10.MSSQLSERVER \ MSSQL \ DATA \ MySchool. mdf ',
Size = 10 MB,
Filegrowth = 1 MB,
Max size = 100 MB
)
Log on
(
Name = 'myschool _ log ',
FileName = 'd: \ Program Files \ Microsoft SQL Server \ MSSQL10.MSSQLSERVER \ MSSQL \ DATA \ MySchool_log.ldf ',
Size = 3 MB,
Filegrowth = 10%

)

Table creation:

Create table Test (id int identity (1, 1) primary key, name nvarchar (10) not null, age int not null, gender char (2) not null );

Delete table:

Drop table Test;

Insert data:

Insert into Test (name, age, gender) values ('xiao Zhao ', 99, 'female ');

Query data:

Select name from Test where gender = 'male ';

Modify data:

Update Test set age = age + 5 where gender = 'femal ';

Delete data:

Delete from Test where age> 50;

The difference between delete from Test; and truncate table Test;: 1. The truncate statement is very efficient. 2. The truncate statement resets the automatic number in the table to the default value.

The following are the categories and differences of data types:

Category

Remarks and instructions

Type

Description

Binary data type

Store non-Child characters and text data

Image

Used to store images

Text Data Type

Character data includes a combination of any letters, symbols, or numbers

Char, 8000

Non-Unicode character data of a fixed length. A fixed-length string is more efficient than a variable-length string. When the data length is fixed, the fixed-length string is preferred. The Hong Kong server saves the process of calculating the length and improves the efficiency.

Varchar, 8000

Variable-length non-Unicode data

Nchar, 4000

Unicode data of a fixed length

Nvarchar, 4000

Variable-length Unicode data

Text

Varchar (max)

Store long text information (pointer, 2G)

Varchar (max), a large string type can store a lot of characters, but such data DBMS often save them to a separate space, this leads to a slow data storage and loading speed. Therefore, do not use it unless necessary for an American server.

Ntext

Nvarchar (max)

Replace Nvarchar (max)

Date and Time

Enter the date and time in single quotes

Datetime

Date and Time

Digital Data

This data only contains numbers, including positive numbers, negative numbers, and scores.

Int

Smallint

Integer

Float

Real

Number

Currency Data Type

It is used for decimal currency values. The data types of money and smallmoney are precise to one thousandth of the currency units they represent.

Money

Bit Data Type

Indicates yes/no data

Bit

Store boolean data types