Database Application diagram 1

Database Application diagram 1

I have been exposed to a large number of database contents in my previous years. because the company has a large number of software users, it needs to use databases to manage users well. in today's fierce business competition, whether an enterprise can have its own database system is highly managed. small enterprises also need databases as their own support. in general, it is very convenient to use the database and get twice the result with half the effort.

Let's start with the most basic operations.

Enter:Services. MSC

 

I. Start the service

 

2. Two authentication methods for database Login

Another authentication method is SQL Server Authentication.

Steps not available for SA:

1. Log On with windows, right-click "instance", "properties", and "security", and set "server authentication method"

For "SQL Server and Windows", click OK. "Restart the service ".

2. Enable the SA account. After connecting to the database with windows, click "security" → "Login Name" → right-click "sa" attribute,

→ Status → enable. After enabling, find the "general" tab and modify the SA password.

 

Instance

 

Enable SA account

 

Create a database:

 

3. Create a database

How to Create a table?

 

4. Create a table

 

 

5. How to Set automatic numbers

 

6. Modify the created table

 

7. add data to the table

 

8. Common Data Types in Databases

Lists the data types in common databases.

The following is a brief introduction.

Sometimes the image information is stored in the database, and the binary image type is used in this case.

 

Char (10) cannot store more, for example, 11, but it is OK if it is missing. The occupied space is fixed.

We recommend that you use nchar (10) for gender storage.

Char and nchar all with no VaR in front indicate fixed length.

 

Varchar and nvarchar indicate the variable length and the variable length.

Varchar (10); 2. during actual storage, the length is calculated dynamically based on the actual data,

If the length exceeds the pre-declared length, an error is returned. If the length is not enough, re-calculate the value based on the actual length.

Generally, a variable length is used for an address.

 

Nchar (10)

Differences between char (10) and nchar (10:

Char (10) 'aaaaaaaaaaa', 'Look for look' occupies 10 bytes

Nchar (10) 'aaaaaaaaaaa', 'Look for it, look for it ', accounting for 20 bytes

When will n be used? The system uses Chinese information and char.

However, if you want to execute the command in an English operating system, we recommend that you use the command with N.

 

 

Their maximum value: varchar (8000)

Char (8000)

 

Nvarchar (4000)

Nchar (4000)

 

Varchar (10)

Nvarchar (10)

Varchar (max)Article.

Nvarchar (max)

 

This is not recommended after sql2005.

Text

Ntext

 

Database separation and Addition

 

9. Separation

 

10. Separation 2

 

11. Additional

 

12. Attach 2

The automatic number will always go forward and never go back.

The following describes how to useCodeCreate a database

 

 

13. Create a database

14. database creation code

Create a table:

 

15. Create a table in the database

 

16. Go statements

If I want to copy my database scripts to my colleagues, but I am using sql2005 and sql2008, I cannot use separation, attached. take the following steps:

 

17. Step 1 of script generation

Select next

Select: compile all scripts for the entire database.

 

18. Step 2

Of course, there are some items that we can choose from. In this case, we will not describe them one by one.

Some minor problems may occur when attaching this part. Can you ask me if you have any questions?

 

CTRL + K + C comments;

CTRL + K + u uncomment;

 

The result is an attempt to use Ctrl + R

 

19. How to view data in a table

The following describes how to insert data.

 

20. insert data

Excluding the automatic numbers, do not manually insert those columns.

 

21. insert data not empty

 

22. Translated

Data must be inserted into columns that cannot be empty. Otherwise, an error is returned.

 

23. Insert automatic ID

 

24. Insert multiple rows of data

Pay attention to this writing method. Union will be detailed later.

 

25. export data from the current table to a new table

 

26. Create a table with the same structure as the source table but without data

 

New Content

 

Add suggestion

27. insert data to an existing table

 

18th, insert Chinese, add n

The following describes common update Methods:

 

29. Update the column

 

Thirty. Update multiple columns of data at the same time

Let's talk about this first.

 

. Conditional query rows

 

Limit column and row Query

 

33. Update the specified row and column at the same time.

Note that you must back up the data before updating the data. Otherwise, it may be troublesome. You can make a backup and restore.

 

. Both update conditions are met.

Pay attention to the use of the logical operators not and or in the database; Priority: Not and or

 

35. Add 1 to all ages.

It is better to add 1 to the database or write it as a graph. If this is always the case, you may not be able to use it in another place. Parentheses can change the priority.

The following describes two ways to delete data:

 

36. Delete the specified data

 

. Differences between the two deletion statements

The comments in the figure are the differences between them.

The following describes some constraints:

Before creating a constraint, delete all the previous data because the previous data is invalid.

 

Step 1 of building constraints

 

. Step 2 of constraints

 

Forty. Step 3 of constraints

Click: Expression

Input constraints

Click: OK

 

 

XI. constraint execution

 

. Set other constraints

 

Forty-three constraints: Get the current database time

Other forms except check constraints:

Default constraint:

 

Forty-four, modify the default value

Unique Constraint

 

Forty-five, unique constraint, such as the ID card number cannot be the same

Forty-six, fill in the content with the unique constraint

If the number of departments I enter is 30, but the number of departments in the department table is not 30. At this time, I need to set the foreign key.

Foreign key constraints:

 

47. Create foreign key constraints

 

Forty-eight foreign key relationship settings

Point: Table and column standards

Set the foreign key table and associated ID of the primary key table.

Click OK to automatically generate the ID and name

 

 

Forty-nine, set the primary and Foreign keys

We can clearly see that the primary key is yellow and the foreign key is gray.

Tables that are not referenced by foreign keys can be deleted, but referenced tables cannot be deleted.

Since the establishment of the relationship between the primary and external building will cause a series of troubles, we generally do not build. HoweverProgramTo maintain the external relationship.

 

50. prelude to deleting the external creation Constraints

 

 

51. Delete the primary and external creation constraint 1

 

Delete external primary key constraint 2-cascade Delete

 

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