SQL Learning notes one SQL basic knowledge _mssql

Commonly used segment type bit (0 and 1), Datetime,int,varchar,nvarchar (may contain Chinese nvarchar)

The difference between Varchar,nvarchar and char (n) char (n) is less than the part of the length n is padded with spaces.

In SQL statements, strings are enclosed in single quotes.

SQL statements are not case sensitive. Insensitivity refers to the SQL keyword, string value, or sensitivity.

Simple INSERT statement INSERT into person (id,name,age) VALUES (1, ' Jim ', 20)

Common int and uniqueidentifier key data types

Identity specification: Automatically fills values for primary keys. Set the field is identity column to Yes, a table can have only one identity column

The GUID algorithm is an efficient algorithm that can produce a unique identification. NET, the method for generating GUIDs: Guid.NewGuid () returns the GUID type. The function that generates the GUID in SQL Server is NEWID ()

Data inserted with a GUID is inconsistent with the displayed data.



Data Update

Update one column: Update person set age = 30

Update multiple columns: updage person set age = 30,name = ' Tom '

Update part of data: Update person set age = 30,where Name = ' Tom '

Note that the judgment in SQL is a single =, not = =



Delete all data in a table: Delete from person (drop statement deletes table)