Drop a Column and its Constraints and Indexes

  • Andy B.

    SSC Eights!

    Points: 890

    Comments posted to this topic are about the item Drop a Column and its Constraints and Indexes


    Enjoy!

    A Brown

    Manage all of your backups in one simple job using this script.

  • Tech_Newbie

    SSC Veteran

    Points: 215

    PLEASE HELP: I AM TRYING TO USE THE FOLLOWING SCRIPT TO :

    1. FOR EACH TABLE IN A GIVEN DATABASE (I am using a cursor for this)

    2. FIND IF A COLUMN OF NAME "row_id" exists

    3. IF it does, delete it

    4. if it doesnt, proceed to next table

    Right now I am getting error messages when it comes to a table where the column does not exist, it simply stops because the drop statement fails - what am I doing wrong ???????????????????????????

    code:

    --ALTER TABLES SCRIPT

    --change the line marked *** to suit your update needs....

    IF EXISTS (SELECT *

    FROM sysobjects o WITH(NOLOCK),

    syscolumns b WITH(NOLOCK)

    WHERE o.[id] = b.[id] AND b.name = 'row_id'

    AND O.name = ''+o.name)

    BEGIN

    DECLARE tableNamesCursor CURSOR

    FOR

    --***

    --select 'ALTER TABLE ['+ o.name+ '] ADD row_id as '+o.name+'+'ID'

    -- CONSTRAINT AddDateDflt'+ cast(o.id as varchar(10))+ ' DEFAULT getdate() WITH VALUES'

    -- removes the TimeStamp column, and constraint from all tables

    select 'ALTER TABLE ['+ o.name+ '] DROP COLUMN row_id'

    from sysobjects o, sysindexes i

    where i.id = o.id

    and indid in(0,1)

    and o.name not like 'sys%'

    and o.name not like 'dt%'

    order by o.name

    OPEN tableNamesCursor

    DECLARE @alterTableSql nvarchar(400)

    FETCH NEXT FROM tableNamesCursor INTO @alterTableSql

    WHILE (@@FETCH_STATUS <> -1)

    BEGIN

    IF (@@FETCH_STATUS <> -2)

    BEGIN

    print @alterTableSql

    exec sp_executesql @alterTableSql

    END

    FETCH NEXT FROM tableNamesCursor INTO @alterTableSql

    END

    CLOSE tableNamesCursor

    DEALLOCATE tableNamesCursor

    END

  • Lau-765114

    Old Hand

    Points: 345

    Andy's script is great but not so clean.

    I ran it against a SQL2000 database trying to drop a column along with all its constraints/indexes. Here are the issues I faced:

    1. The criteria of the constraints cursor should be changed to

    WHERE ((OBJECTPROPERTY(Cons.[id],'IsConstraint') = 1

    OR (OBJECTPROPERTY(Cons.[id],'IsPrimaryKey') = 1))

    AND Cons.info = Cols.colid)

    AND Cons.parent_obj = @tableID

    as you don’t want to drop the primary key if the given column is not part of it.

    2. The join criteria for the sysindexes table in the indexes cursor should include a fourth line as follows:

    INNER JOIN dbo.sysindexkeys SIK WITH (NOLOCK)

    ON SIK.id = SC.id

    AND SIK.colid = SC.colid

    AND SIK.indid = SI.indid

    otherwise the cursor will return duplicate rows.

    3. The second line of the where criteria of the indexes cursor must be changed as follows:

    WHERE SI.indid !=0

    AND ISNULL(OBJECTPROPERTY(OBJECT_ID(SI.name),'IsConstraint'), 0) = 0

    AND SC.id = @tableID

    AND SC.name = @column

    as many (valid) rows return a NULL value there

    4. The statement that drops the index should be:

    SELECT @sql = N'DROP INDEX '+@table+'.'+@index

    5. The commit/rollback block should be:

    IF @@TRANCOUNT > 0

    BEGIN

    IF @rollback = 0

    COMMIT TRANSACTION

    ELSE

    ROLLBACK TRANSACTION

    END

    as you want to commit/rollback only if a transaction has been started.

    These are all the things I had to change in order to have the script running properly, according to my testing. I hope this helps others, too, enjoying Andy’s great script !

  • milvards

    SSC Enthusiast

    Points: 172

    Can anyone help on this.

    I try to run this on SQL Server 2005 and it don't work. Even after lau's changes.

    The code for the cursor cur_constraints does not return anything.

    I don't have enough knowledge two find out whats wrong, but by running the select on it's own I can see that the Cons.info always contains 0 (zero). Without the AND Cons.info = Cols.colid, it returns all constraint rows for the table.

    Does anyone out there have the skills to tell me how to fix this.

    Thank you.

  • Lau-765114

    Old Hand

    Points: 345

    Milvards, you are right, the script doesn't work for SQL2005 and I need it, too, for both 2000 and 2005 versions.

    I had a couple of attempts on this but failed. I'm planning to give it one more try (hopefully, sooner than later) and, if I'll succeed, I'll post an updated script on this thread for your and everybody's use.

  • milvards

    SSC Enthusiast

    Points: 172

    Hi Lau.

    I made it work at last using some code I found on the internet (credit to a chap from India called chiragkhabaria).

    Replace the code for cur_constraints with this:

    DECLARE cur_constraints CURSOR FOR

    SELECT Cons.XType, Cons.[Name] FROM SysObjects AS Cons

    INNER JOIN (Select [Name],[ID] From SysObjects Where XType = 'U) AS Tab ON Tab.[ID] = Cons.[Parent_Obj]

    INNER JOIN sysconstraints ON sysconstraints.Constid = Cons.[ID]

    INNER JOIN SysColumns Col ON Col.[ColID] = sysconstraints.[ColID] AND Col.[ID] = Tab.[ID]

    WHERE (Tab.[Name] = @table) AND (Col.[Name] = @column)

    It can probably be written in a better way but it looks like it does the job.

    M

  • Lau-765114

    Old Hand

    Points: 345

    Thanks, man, I hope it works (for both 2000 and 2005). I'll give it a try today.

    (I really don't care how it looks as long as it does the job properly).

  • Lau-765114

    Old Hand

    Points: 345

    Thank you, Milvards, thank you, Chiragkhabaria 😉

    I got to the same conclusion: the script works fine for both SQL2000 and 2005 if you apply the change mentioned above by Milvards.

    The only case I found when it doesn't work is when the specified column is part of PK but I guess this is something we could live with.

    Thanks again to all for this, especially to Andy.

  • aoa-1120895

    SSC Journeyman

    Points: 85

    The code in the article did not work for me, I had to rewrite the stored procedure, the below works

    CREATE PROCEDURE

    DropColumnConstraints

    @TableName varchar(256),

    @ColumnName varchar(256)

    AS

    BEGIN

    declare @sql_value nvarchar(4000);

    declare @obj_name varchar(256);

    declare name_cursor cursor for

    select

    objs.name

    from dbo.sysconstraints const

    inner join dbo.syscolumns cols

    on const.colid = cols.colid

    and const.id = cols.id

    inner join dbo.sysobjects objs

    on objs.id = const.constid

    where cols.id = OBJECT_ID(@TableName)

    and cols.name = @ColumnName

    OPEN name_cursor

    FETCH NEXT FROM name_cursor

    INTO @obj_name

    WHILE @@FETCH_STATUS = 0

    BEGIN

    set @sql_value = ('alter table ' + @TableName +' drop constraint '+@obj_name);

    print 'Dropping '+@obj_name;

    execute sp_executesql @sql_value;

    FETCH NEXT FROM name_cursor

    INTO @obj_name;

    END

    CLOSE name_cursor

    DEALLOCATE name_cursor

    end

    go

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