Database Series Learning (ii)-creation and management of data tables

1. Data type

A: Integer type

Bit,int,smallint,tinyint

"Relative to the number of operating system bits"

B: Numeric type

Decimal,numeric,money,smallmoney,float,real

"Save Decimal"

C: Character-related types

Char,varchar,text,nchar,nvarchar,ntext

D: Date Time Type

DateTime (Accurate to 0.01 seconds), smalldatetime (accurate to minutes), timestamp

E: Binary type

Image

"By image, video to binary, save to database"

2. Managing data tables with SQL statements

A: Create A data table

B: Define a non-null constraint

C: Define default values

D: Define primary key

E: Define foreign keys

F: Modify an existing data table

G: Delete data table

"If you have a primary foreign key relationship, you must first delete the foreign key table"

H: Solution for limited operation

If you delete a field F1 in table T, you can first create a table that has the same structure as the table T, with the only difference being the missing field F1.

The data in table T is then imported into T1, then the T is deleted, and the table T1 is renamed to T.

Database Series Learning (ii)-creation and management of data tables