SQL Server Cursor Example

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 Example SQL Server Cursor
Here is an example cursor
DECLARE @name VARCHAR(50) -- database name  DECLARE @path VARCHAR(256) -- path for backup files  DECLARE @fileName VARCHAR(256) -- filename for backup  DECLARE @fileDate VARCHAR(20) -- used for file name 
SET @path = 'C:\Backup\'  
SELECT @fileDate = CONVERT(VARCHAR(20),GETDATE(),112) 
DECLARE db_cursor CURSOR FOR  
SELECT name FROM MASTER.dbo.sysdatabases WHERE name NOT IN ('master','model','msdb','tempdb')  
OPEN db_cursor   FETCH NEXT FROM db_cursor INTO @name   
WHILE @@FETCH_STATUS = 0   BEGIN   
       SET @fileName = @path + @name + '_' + @fileDate + '.BAK'  
       BACKUP DATABASE @name TO DISK = @fileName  

       FETCH NEXT FROM db_cursor INTO @name   END   

CLOSE db_cursor   DEALLOCATE db_cursor

SQL Server Cursor Components

Based on the example above, cursors include these components:
  • DECLARE statements - Declare variables used in the code block
  • SET\SELECT statements - Initialize the variables to a specific value
  • DECLARE CURSOR statement - Populate the cursor with values that will be evaluated
    • NOTE - There are an equal number of variables in the DECLARE CURSOR FOR statement as there are in the SELECT statement.  This could be 1 or many variables and associated columns.
  • OPEN statement - Open the cursor to begin data processing
  • FETCH NEXT statements - Assign the specific values from the cursor to the variables
    • NOTE - This logic is used for the initial population before the WHILE statement and then again during each loop in the process as a portion of the WHILE statement
  • WHILE statement - Condition to begin and continue data processing
  • BEGIN...END statement - Start and end of the code block
    • NOTE - Based on the data processing multiple BEGIN...END statements can be used
  • Data processing - In this example, this logic is to backup a database to a specific path and file name, but this could be just about any DML or administrative logic
  • CLOSE statement - Releases the current data and associated locks, but permits the cursor to be re-opened
  • DEALLOCATE statement - Destroys the cursor

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