SQL statement of SQL server creates database

Let's explain first Sql The function of symbols in sentences , Otherwise, when you see this series of representations, you will not know how to write them in the database and , This symbol book does not need to be written into the database , Just write the contents
[ ]	This square bracket indicates whether this item can be written or not
{ }	Braces indicate that this item must be written
|	The vertical bar is used to separate each item , Indicates one of the options
[, ...n]	Indicates that the previous item can be n Secondary repetition ,“ , ” Used to separate each item
<>	What is in angle brackets is usually a label , Others represent grammatical chunks , In other words, the contents of this label can be written in multiple
()	If expressed in parentheses , When writing code, the parentheses are also It should be written into the code Of , He is not a sign , Do not omit
in addition , stay sql In the sentence is Case insensitive Of ！ Generally, the characters specified by the system will be capitalized , But I was confused when I saw the capital letters , So I usually use lowercase , Also use lowercase here , It's more comfortable to look at and remember .

One more point , In use SQL When writing the database, you will not know where the code is written , Actually , Or write code directly in the new query , But note that the database code that has been executed cannot be executed again , Because it has been created , You cannot create a database with the same name again （ The same is true of data tables ）. Then select , Re execution , It can be executed paragraph by paragraph .

sql Statement create database

creat  database  < Database name >  （ Directly define the name when building the database , Don't have to add <>）

[ ON         -- ON It is used to store data files

        [ < filespec >[ , . . . n ] ]       --  there filespec Is a label block , It refers to data files or log files

]

[ Log on              -- Log on It is used to store log files    

        {         <filespec>[ , . . . n ]      }    

]

among , Data files or log files include ： file name 、 File storage location 、 Initial size 、 The maximum capacity 、 Growth capacity , Where initial size 、 The maximum capacity 、 Increasing capacity can be omitted , It will be established by default .

-- File format

[ primary ]       -- Specify the file as the main file , A database can only have one master file , If not, the first file will be the main file by default

(

        name =  file name ,

        filename = ' File name storage location  ' ,

        [ , size = n ]

        [ , maxsize = { m | unlimited } ]     --n,m It can be directly numerical , The default unit is MB

        [ , filegrowth = g ]    -- Increasing capacity can be used KB、MB perhaps % To represent the

)

-- When writing code , To write this section to   Yes < filespec > label The location of

Nothing can be understood by a piece of code  

CREATE DATABASE Librarys
ON
(
	NAME = library,
	FILENAME = 'E:\Library.mdf',
	SIZE = 5,
	MAXSIZE = 20
)
LOG ON
(
	NAME = library_log,
	FILENAME = 'E:\Librarylog.ldf',
	SIZE = 1,
	MAXSIZE = 10
)

SQL Statement to modify the database

After creating a database, you can't directly change the content and re create it again （ Not deleted ）, So we need to write additional code to modify the database

alter  database  < Database name >

{

        Add  File  < filespec > [ , . . . n ] [ to filegroup  Filegroup name ]  --  Add a new file

     |    remove file  file name      -- Delete this file

     |    modify file  < filespec >     -- Make changes to the file ,Ps： Specify in the file name, You can only change size or  maxsize or filegrowth, and size The size of is larger than the original

     |    Add log file  < filespec >     -- Add log file

     |    modify name =  New database name        -- Rename the database

}

Delete database

Drop database  Database name   [ , . . . n ]   -- Delete database

Using this statement to delete will delete all the contents of this database file on the disk , And the confirmation message will not appear before deletion , So be careful to use this statement .