Shulou(Shulou.com)06/01 Report--

1. Database file type:

① data file

Main data file: suffix .MDF, one and only one, created by default, containing startup information and data objects

Secondary data file: suffix .ndf, can have any one, default none

File stream data: storing pictures, audio and other files

② transaction log file: suffix .ldf, at least one, created by default, a SQL statement that records all transactions, using the

In restoring the database

2. Create and expand the database

File size: has an initial size, expandable, minimum unit 1MB

Growth mode: ① by percentage ② by MB

Data size can be limited: method: ① limit size ② does not limit size

3. Shrink the database: free up unused space

Method: ① manual contraction

Shrink the database: cannot be lower than the initial size

Shrink file: can be lower than the initial size, the smallest unit is 1m

② automatic contraction

Database properties, which can be set for automatic contraction

4. Detach and attach databases

Detach: remove the database from the instance to make it easier to move or copy the database

Attach: add a database to the instance

Delete: remove the database from the instance and delete the data file, only the user database can be deleted

5. Data type:

Exact number: int: integer

Bit: there are only 0 or 1 or NULL values, and only 0 and 1 values can be entered

Decimal: numeric

Money: currency valu

Approximate numbers: float, real

String: char: fixed length, specified column length

Varchar: variable length, specify maximum size

Text: large number of characters

Nchar, nvarchar, ntext: Unicode character, double byte

Binary characters: binary

Date and time: date date time time datetime date and time

6. Create tables:

① column name ② data type ③ whether null values are allowed or not these three points are necessary

④ default value: no value specified for the column, use default value

⑤ identifier column: a column that automatically generates ordinal values, which cannot be entered or changed, and there can be at most one.

Three elements: the data type is numerical

Seeds: initial valu

Increments: step size, growth valu

⑥ check constraints (check): limit acceptable values

⑦ sets the primary key

⑧ set foreign key

7. Insert data:

Insert into table name values ('value 1', 'value 1', 'value 2', 'value', etc. )

8. Update the data:

Update table name set column name = 'new value' where condition

9. Delete data:

① delete: you can conditionally delete part of the data, save the log, restore it, do not reset the identity column, and delete it with foreign keys.

Constrained data table

② truncate: can only empty the entire table, do not save the log, cannot be recovered, reset the identity column to 0, and cannot delete the foreign key.

List of bundles

Command: delete from table name where condition

Truncate table table name

10. Delete libraries and tables:

Drop database library name

Drop table table name

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