Solved

Drop a default when dropping a column

Posted on 2004-08-04
7
1,225 Views
Last Modified: 2012-08-13
I'm programmatically allowing users to add and drop columns

Its working OK but when a column has been given a default, the

    alter table drop column

command fails because the default constraint exists.

Is there a way to make it ignore defaults and just drop the column and any defaults with it ?

Defaults are never shared between columns in this DB

thanks
0
Comment
Question by:plq
  • 3
  • 2
  • 2
7 Comments
 
LVL 14

Assisted Solution

by:Thandava Vallepalli
Thandava Vallepalli earned 250 total points
ID: 11714150
Hi,

Here is the rule... you have to drop the default constraint first before droping the column...

----------------
DROP { [CONSTRAINT] constraint_name | COLUMN column_name }

Specifies that constraint_name or column_name is removed from the table. DROP COLUMN is not allowed if the compatibility level is 65 or earlier. Multiple columns and constraints can be listed. A column cannot be dropped if it is:

A replicated column.

Used in an index.

Used in a CHECK, FOREIGN KEY, UNIQUE, or PRIMARY KEY constraint.

Associated with a default defined with the DEFAULT keyword, or bound to a default object.


itsvtk
0
 
LVL 14

Expert Comment

by:Thandava Vallepalli
ID: 11714158
so here is your dml statements


1. alter table drop constraint <defult_val_constraint_name>

2. alter table drop column

itsvtk
0
 
LVL 9

Expert Comment

by:crescendo
ID: 11714165
Use

sp_unbindefault 'YourTable.YourColumn'

to get rid of the default.
0
What is SQL Server and how does it work?

The purpose of this paper is to provide you background on SQL Server. It’s your self-study guide for learning fundamentals. It includes both the history of SQL and its technical basics. Concepts and definitions will form the solid foundation of your future DBA expertise.

 
LVL 9

Accepted Solution

by:
crescendo earned 250 total points
ID: 11714175
With sp_unbindefault you don't need to know the name of the default, just the name of the table and column, so it's easier than dropping the default by name.
0
 
LVL 8

Author Comment

by:plq
ID: 11714186
Yes I wouldn't know the name of the default - I'll give it a try

thanks
0
 
LVL 8

Author Comment

by:plq
ID: 11714602
I'm getting this error message

Server: Msg 15049, Level 11, State 1, Procedure sp_unbindefault, Line 98
Cannot unbind from 'Asset.spcTestField'. Use ALTER TABLE DROP CONSTRAINT.


Here's the program generated script

set ansi_warnings off
exec sp_unbindefault 'Asset.spcTestField'
alter table Asset drop column spcTestField
0
 
LVL 8

Author Comment

by:plq
ID: 11715195
I found this view on the net

create view v_DEFAULT_CONSTRAINT
as
select      db_name()                        as CONSTRAINT_CATALOG
      ,t_obj.name                         as TABLE_NAME
      ,user_name(c_obj.uid)                  as CONSTRAINT_SCHEMA
      ,c_obj.name                        as CONSTRAINT_NAME
      ,col.name                        as COLUMN_NAME
      ,col.colid                        as ORDINAL_POSITION
      ,com.text                        as DEFAULT_CLAUSE

from      sysobjects      c_obj
join       syscomments      com on       c_obj.id = com.id
join       sysobjects      t_obj on c_obj.parent_obj = t_obj.id  
join    sysconstraints con on c_obj.id      = con.constid
join       syscolumns      col on t_obj.id = col.id
                  and con.colid = col.colid
where
      c_obj.uid      = user_id()
      and c_obj.xtype      = 'D'

GO


That enabled me to select the name of the default based on table and column name, and then I could drop the default using "alter table drop constraint"




0

Featured Post

PRTG Network Monitor: Intuitive Network Monitoring

Network Monitoring is essential to ensure that computer systems and network devices are running. Use PRTG to monitor LANs, servers, websites, applications and devices, bandwidth, virtual environments, remote systems, IoT, and many more. PRTG is easy to set up & use.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction In my previous article (http://www.experts-exchange.com/Microsoft/Development/MS-SQL-Server/SSIS/A_9150-Loading-XML-Using-SSIS.html) I showed you how the XML Source component can be used to load XML files into a SQL Server database, us…
Why is this different from all of the other step by step guides?  Because I make a living as a DBA and not as a writer and I lived through this experience. Defining the name: When I talk to people they say different names on this subject stuff l…
Via a live example, show how to extract insert data into a SQL Server database table using the Import/Export option and Bulk Insert.
Via a live example, show how to setup several different housekeeping processes for a SQL Server.

777 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question