SQL Server Add fields, modify fields, modify types, modify default values

1. Modify the field name:

ALTER TABLE name rename column A to B

2. Modify the field type:

ALTER TABLE name ALTER COLUMN field name type NOT NULL

3. Modify the field default value
ALTER TABLE name add default (0) for field name with values

If the field has a default value, you need to remove the constraint for the field before adding a new default value,

Select C.name from Sysconstraints a
INNER JOIN syscolumns B on a.colid=b.colid
INNER JOIN sysobjects C on a.constid=c.id
where a.id=object_id (' Table name ')
and b.name= ' field name '

To remove a constraint from a constraint name

ALTER TABLE name DROP CONSTRAINT constraint name

Add a new default value to a field based on the table name

ALTER TABLE name add default (0) for field name with values

4. Add Field:

ALTER TABLE name add field name type NOT NULL default 0

5. Delete fields:

ALTER TABLE Name drop column field name;

SQL Server Add fields, modify fields, modify types, modify default values