copy FOREIGN KEY constraints from one DB to other - sql-server

Question

I have a local db which has FOREIGN KEY constraints.
The live version of this websites DB, does not have any of these FOREIGN KEY constraints.
How can I "copy/paste", import/export ONLY the FOREIGN KEY constraints from one db to the other?
I do NOT want to copy any data, only the constraints.
Thanks

Answer 1

You could use this script I found at http://www.siusic.com/wphchen/how-to-script-out-all-the-foreign-keys-of-a-table-106.html. Replace tablename1 and tablename2 with the list of tables you wish to get the foreign keys for.
select 'ALTER TABLE '+object_name(a.parent_object_id)+
' ADD CONSTRAINT '+ a.name +
' FOREIGN KEY (' + c.name + ') REFERENCES ' +
object_name(b.referenced_object_id) +
' (' + d.name + ')'
from sys.foreign_keys a
join sys.foreign_key_columns b
on a.object_id=b.constraint_object_id
join sys.columns c
on b.parent_column_id = c.column_id
and a.parent_object_id=c.object_id
join sys.columns d
on b.referenced_column_id = d.column_id
and a.referenced_object_id = d.object_id
where object_name(b.referenced_object_id) in
('tablename1','tablename2')
order by c.name

Answer 2

I needed to do something similar, where I needed the same foreign keys on multiple servers, except some had already been added. So I added a "IF NOT EXISTS" check to the beginning of the creation statements:
SELECT N'
IF NOT EXISTS (SELECT * FROM sys.foreign_keys
WHERE object_id = OBJECT_ID(''' + QUOTENAME(fk.name) + ''')
AND parent_object_id = OBJECT_ID(''' + QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name) +''')
)
BEGIN
ALTER TABLE '
+ QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)
+ ' ADD CONSTRAINT ' + QUOTENAME(fk.name)
+ ' FOREIGN KEY (' + STUFF((SELECT ',' + QUOTENAME(c.name)
-- get all the columns in the constraint table
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.parent_column_id = c.column_id
AND fkc.parent_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'), 1, 1, N'')
+ ') REFERENCES ' + QUOTENAME(rs.name) + '.' + QUOTENAME(rt.name)
+ '(' + STUFF((SELECT ',' + QUOTENAME(c.name)
-- get all the referenced columns
FROM sys.columns AS c
INNER JOIN sys.foreign_key_columns AS fkc
ON fkc.referenced_column_id = c.column_id
AND fkc.referenced_object_id = c.[object_id]
WHERE fkc.constraint_object_id = fk.[object_id]
ORDER BY fkc.constraint_column_id
FOR XML PATH(N''), TYPE).value(N'.[1]', N'nvarchar(max)'), 1, 1, N'') + ')
END'
FROM sys.foreign_keys AS fk
INNER JOIN sys.tables AS rt -- referenced table
ON fk.referenced_object_id = rt.[object_id]
INNER JOIN sys.schemas AS rs
ON rt.[schema_id] = rs.[schema_id]
INNER JOIN sys.tables AS ct -- constraint table
ON fk.parent_object_id = ct.[object_id]
INNER JOIN sys.schemas AS cs
ON ct.[schema_id] = cs.[schema_id]
WHERE rt.is_ms_shipped = 0 AND ct.is_ms_shipped = 0;
If you do not want the "IF NOT EXISTS" checks (they really shouldn't matter), just delete the top 5 lines and add "SELECT N' " right before the "BEGIN", like this:
SELECT N'BEGIN
ALTER TABLE '
+ QUOTENAME(cs.name) + '.' + QUOTENAME(ct.name)
-- I found the core of this query online somewhere and I've been modifying it for some time. Credit to them for putting most of it together...