Preserve SQL Indexes While Altering Column Datatype

Question

I have a smalldatetime column that I need to alter to be a datetime column. This is something that will be part of an install process, so it cannot be a manual procedure. Un

Answer 1

The best thing to do is to create a procedure that returns the index script of a given table / column. So you can remove the indexes just from the column being altered and not all indexes from the table, whereas creating indices can be somewhat expensive.

1. Stores the result of the procedure in a datatable
2. Delete the indices of the column
3. Modify your column

4. Rebuild the indexes stored in the datatable

   -- objective   : Generates indices scripting using specified column
   -- Parameters : 
   --     @Tabela  -> Name of the table that the column belongs to 
   --     @Coluna -> Name of the column that will be searched for the indices to generate the script
   --Use: proc_ScriptIndexColumn 'TableName', 'ColumnName'
   
   SET ANSI_NULLS ON
   GO
   SET QUOTED_IDENTIFIER ON
   GO
   Create Proc proc_ScriptIndexColumn (@Tabela VARCHAR(4000), @Coluna VARCHAR(4000)) 
   AS 
   BEGIN     
        DECLARE @isql_key VARCHAR(4000), 
            @isql_incl VARCHAR(4000), 
            @tableid INT, 
            @indexid INT         
    DECLARE @tablename VARCHAR(4000), 
            @indexname VARCHAR(4000)         
    DECLARE @isunique INT, 
            @isclustered INT, 
            @indexfillfactor INT         
    DECLARE @srsql VARCHAR(MAX)        
    DECLARE @ScriptsRetorno TABLE 
            (Script VARCHAR(MAX))        
    DECLARE index_cursor CURSOR  
      FOR 
        SELECT tablename = OBJECT_NAME(i.[object_id]), 
               tableid       = i.[object_id], 
               indexid       = i.index_id, 
               indexname     = i.name, 
               isunique      = i.is_unique, 
               CASE I.type_desc 
                    WHEN 'CLUSTERED' THEN 1 
                    ELSE 0 
               END                     AS isclustered, 
               indexfillfactor = i.fill_factor                  
        FROM   sys.indexes             AS i 
               INNER JOIN SYSOBJECTS   AS O 
                    ON  I.[object_id] = O.ID 
               INNER JOIN sys.index_columns AS ic 
                    ON  (ic.column_id > 0 
                            AND (ic.key_ordinal > 0 
                                    OR ic.partition_ordinal = 0 
                                    OR ic.is_included_column != 0 
                                )) 
                    AND (   ic.index_id = CAST(i.index_id AS INT) 
                            AND ic.object_id = i.[object_id] 
                        ) 
               INNER JOIN sys.columns  AS sc 
                       ON  sc.object_id = ic.object_id 
                    AND sc.column_id = ic.column_id 
        WHERE  O.XTYPE = 'U' 
               AND i.typE = 2 /*Non clustered*/ 
               AND i.is_unique = 0 
               AND i.is_hypothetical = 0 
               AND UPPER(OBJECT_NAME(i.[object_id])) = UPPER(@Tabela) 
               AND UPPER(sc.name) = UPPER(@Coluna)       
   
    OPEN index_cursor  
    FETCH NEXT FROM index_cursor INTO @tablename,@tableid, @indexid,@indexname ,  
    @isunique ,@isclustered , @indexfillfactor       
    WHILE @@fetch_status <> -1 
    BEGIN 
        SELECT @isql_key = '', 
               @isql_incl = ''           
        SELECT @isql_key = CASE ic.is_included_column 
                                WHEN 0 THEN CASE ic.is_descending_key 
                                                 WHEN 1 THEN @isql_key +COALESCE(sc.name, '') + 
                                                      ' DESC, ' 
                                                 ELSE @isql_key + COALESCE(sc.name, '')  
                                                      + ' ASC, ' 
                                            END 
                                ELSE @isql_key 
                            END, 
               --include column  
               @isql_incl = CASE ic.is_included_column 
                                 WHEN 1 THEN CASE ic.is_descending_key 
                                                  WHEN 1 THEN @isql_incl + 
                                                       COALESCE(sc.name, '') + 
                                                       ', ' 
                                                  ELSE @isql_incl + COALESCE(sc.name, '')  
                                                       + ', ' 
                                             END 
                                 ELSE @isql_incl 
                            END 
        FROM   sysindexes i 
               INNER JOIN sys.index_columns AS ic 
                    ON  ( 
                            ic.column_id > 0 
                            AND ( 
                                    ic.key_ordinal > 0 
                                    OR ic.partition_ordinal = 0 
                                    OR ic.is_included_column != 0 
                                ) 
                        ) 
                    AND (ic.index_id = CAST(i.indid AS INT) AND ic.object_id = i.id) 
               INNER JOIN sys.columns AS sc 
                      ON  sc.object_id = ic.object_id 
                    AND sc.column_id = ic.column_id 
        WHERE  i.indid > 0 
               AND i.indid < 255 
               AND (i.status & 64) = 0 
               AND i.id = @tableid 
               AND i.indid = @indexid 
        ORDER BY 
               i.name, 
               CASE ic.is_included_column 
                    WHEN 1 THEN ic.index_column_id 
                    ELSE ic.key_ordinal 
               END           
        IF LEN(@isql_key) > 1 
            SET @isql_key = LEFT(@isql_key, LEN(@isql_key) -1)  
   
        IF LEN(@isql_incl) > 1 
            SET @isql_incl = LEFT(@isql_incl, LEN(@isql_incl) -1)            
        SET @srsql = 'CREATE ' + 'INDEX [' + @indexname + ']' + ' ON [' + @tablename 
            + '] '           
        SET @srsql = @srsql + '(' + @isql_key + ')'              
        IF (@isql_incl <> '') 
            SET @srsql = @srsql + ' INCLUDE(' + @isql_incl + ')'             
        IF (@indexfillfactor <> 0) 
             SET @srsql = @srsql + ' WITH ( FILLFACTOR = ' + CONVERT(VARCHAR(10), @indexfillfactor) 
                + ')'            
        FETCH NEXT FROM index_cursor INTO @tablename,@tableid,@indexid,@indexname,  
        @isunique ,@isclustered , @indexfillfactor           
        INSERT INTO @ScriptsRetorno 
        VALUES 
          (@srsql) 
    END  
    CLOSE index_cursor  
    DEALLOCATE index_cursor   
    SELECT * 
    FROM   @ScriptsRetorno 
   RETURN @@ERROR 
   END