set column to 'not null' in SQL Server

Question

I have a column in a table in a sql server database that I want to set to 'not null'. However, when I execute the query

ALTER TABLE mytable ALTER COLUMN mycolumn INT NOT NULL 

I get an

ALTER TABLE ALTER COLUMN mycolumn failed because one or more objects access this column.

How can I find out what kind of object that is and how do I drop it? The database is very simple and is not supposed to make use of foreign keys, triggers etc.

Answer 1

You could search the sys tables to find out what is dependent on the column. This has its limitations, naturally, but by-and-large should give you some indication of what is dependent on your column:

SELECT
     OBJECT_NAME(D.Object_ID) AS [Dependent]
    ,D.Object_ID
FROM sys.sql_dependencies D
INNER JOIN sys.Columns C
    ON C.object_id = D.referenced_major_id
    AND C.column_id = D.referenced_minor_id
WHERE OBJECT_NAME(C.object_id) = 'MyTable'
AND C.name = 'MyColumn'
;

Once you have the name and object_id of the dependent (it might be a function, a stored procedure, or any number of things) you can go from there.

Answer 2

You might have to drop constraints on the column first,before altering this table.This may be a constraint,index or any thing..below is a small demo showing the same

create table #test
(
id int,
id1 int
)

create index nci_t on #test(id1)
include(id)

alter table #test
alter column id1 varchar(10)

this is the error i got

Msg 5074, Level 16, State 1, Line 2
The index 'nci_t' is dependent on column 'id1'.
Msg 4922, Level 16, State 9, Line 2
ALTER TABLE ALTER COLUMN id1 failed because one or more objects access this column.

also please paste entire error message ,don't strip it