11. SQL Basic Collation (variable)

Variable

Defining variables: Declare @hello varchar (20)

Assignment: Set @hello = ' Hello '

Select (Results box display)/print (message box display) @hello

* Three rows must be run simultaneously

DECLARE @hello varchar (20)

Set @hello = ' Sales Department '

Select *from bumen WHERE name = @hello

When placed in the middle of select and from, can be used as an assignment statement, do not execute the query function (Assignment is the last row of the query to the data)

DECLARE @hello varchar (20)

Set @hello = ' Sales Department '

Select @hello = name from Bumen

Select @hello

Global variables, System variables

Print @ @connections-value only and cannot be assigned (returns the number of connections to SQL Server since the last startup, whether successful or unsuccessful)

Print @ @error-Returns an error when executing the previous SQL statement, returning 0 for Yes

Print @ @language--Returns the language currently in use

Print @ @rowcount--Returns the number of rows affected by the last operation

Print @ @version--Get version information for the database

Ex.

Update bumen set phone= ' 123 ' WHERE name = ' Sales Department '

Select ' This query statement affects the ' +cast (@ @ROWCOUNT as varchar (10)) + ' line ' altogether

DECLARE @text varchar Set @text = ' ab ' JS ' (single quote when escape word trailing characters)

Print @text

11. SQL Basic Collation (variable)