Alter column datatype and default value in a table

i have a table which has 3 columns, one of three is set to default value 0. Now i have to change data type of that particular column and its default value using sql query. am working with sql server 2005. am not getting any prob when i exec ALTER TABLE TABLE_NAME ADD COLUMN [COLUMN_NAME] DATATYPE SIZE CONSTRAINT [CONSTRAINT_NAME] VALUE. but getting probs when exec
ALTER TABLE TABLE_NAME ALTER COLUMN_NAME DATATYPE SIZE [CONSTRAINT NAME] VALUE. Help me, thanx in advance

Quote:

Originally Posted by vijaialphonse

i have a table which has 3 columns, one of three is set to default value 0. Now i have to change data type of that particular column and its default value using sql query. am working with sql server 2005. am not getting any prob when i exec ALTER TABLE TABLE_NAME ADD COLUMN [COLUMN_NAME] DATATYPE SIZE CONSTRAINT [CONSTRAINT_NAME] VALUE. but getting probs when exec
ALTER TABLE TABLE_NAME ALTER COLUMN_NAME DATATYPE SIZE [CONSTRAINT NAME] VALUE. Help me, thanx in advance

Are you sure your columns meet all the criteria described in the ALTER COLUMN notes at http://msdn2.microsoft.com/en-us/library/ms190273.aspx ?
Also not that if you modify the type and/or constraints of a column the data already in the column must meet the new settings.