Wednesday, August 26, 2015

SQL Server script to rebuild all indexes for all tables and all databases

Problem
One of the main functions of a DBA is to maintain database indexes.  There have been several tips written about different commands to use for both index rebuilds and index defrags as well as the differences between index maintenance with SQL Server.  In addition, other tips have been written about using maintenance plans to maintain indexes on all databases.  One of the issues with maintenance plans is that they don't always seem to be as reliable as you would hope and you also sometimes get false feedback on whether the task actually was successful or not.  In this tip we look at a simple script that could be used to rebuild all indexes for all databases.
Solution
The one nice thing about maintenance plans is that it works across multiple databases and therefore you can push out one task to handle the same activity across all of your databases.  The problem that I have seen with maintenance plans is that sometimes they do not work as expected, therefore here is another approach.
The script below allows you to rebuild indexes for all databases and all tables within a database.  This could be further tweaked to handle only indexes that need maintenance as well as doing either index defrags or index rebuilds.
The script uses two cursors one for the databases and another for the tables within the database.  In addition, it uses the INFORMATION_SCHEMA.TABLES view to list all of the tables within a database. 
Because we need to change from database to database we also need to create dynamic SQL code for the queries.  For the DBCC DBREINDEX option we can just pass in the parameters, but for the ALTER INDEX statement we need to build the query dynamically.  Here is the script.
DECLARE @Database VARCHAR(255)   DECLARE @Table VARCHAR(255)  DECLARE @cmd NVARCHAR(500)  DECLARE @fillfactor INT

SET
@fillfactor = 90

DECLARE DatabaseCursor CURSOR FOR 
SELECT
name FROM master.dbo.sysdatabases  
WHERE name NOT IN ('master','msdb','tempdb','model','distribution')   ORDER BY

OPEN DatabaseCursor 

FETCH NEXT FROM DatabaseCursor INTO @Database  WHILE @@FETCH_STATUS =
BEGIN 

   SET
@cmd = 'DECLARE TableCursor CURSOR FOR SELECT ''['' + table_catalog + ''].['' + table_schema + ''].['' +
  table_name + '']'' as tableName FROM ['
+ @Database + '].INFORMATION_SCHEMA.TABLES
  WHERE table_type = ''BASE TABLE'''  

  
-- create table cursor 
  
EXEC (@cmd
  
OPEN TableCursor  

   FETCH NEXT FROM TableCursor INTO @Table  
  
WHILE @@FETCH_STATUS = 0  
   BEGIN  

       IF
(@@MICROSOFTVERSION / POWER(2, 24) >= 9)
      
BEGIN
          
-- SQL 2005 or higher command
          
SET @cmd = 'ALTER INDEX ALL ON ' + @Table + ' REBUILD WITH (FILLFACTOR = ' + CONVERT(VARCHAR(3),@fillfactor) + ')'
          
EXEC (@cmd)
      
END
       ELSE
       BEGIN
          
-- SQL 2000 command
          
DBCC DBREINDEX(@Table,' ',@fillfactor
      
END

       FETCH
NEXT FROM TableCursor INTO @Table  
  
END  

   CLOSE
TableCursor  
   DEALLOCATE TableCursor 

   FETCH NEXT FROM DatabaseCursor INTO @Database  END 
CLOSE
DatabaseCursor  
DEALLOCATE DatabaseCursor


The script will work for both SQL 2000 and higher versions.  For SQL 2000 it uses DBREINDEX and for SQL Server 2005 and higher it uses ALTER INDEX.  Thanks go out to LittlePanthers for providing the code snippet to check the version of SQL Server.

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