Stored Procedure, to create missing foreign keys at target database after comparing both source and target databases.

SYNC_CreateForignKeys.sql

--DROP IF ALREADY CREATED
IF EXISTS (SELECT 1 FROM sys.objects WHERE type = 'P' AND name = 'SYNC_CreateForignKeys')
DROP PROC [dbo].[SYNC_CreateForignKeys]
GO

--CREATE PROCEDURE
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
/*
Stored Procedure, to create missing foreign  keys at target database after comparing  
both source and target databases. 

EXEC [dbo].[SYNC_CreateForignKeys] 'AdventureWork_StableVersion','AventureWork_Target'

*/
CREATE PROCEDURE [dbo].[SYNC_CreateForignKeys]
    (
      @SyncFromDB VARCHAR(200), --Source database name
      @SyncToDB VARCHAR(200) --Target database name
    )
AS 

BEGIN

  CREATE TABLE #AlterStatements (TSQLStmt VARCHAR(MAX))
EXEC('
			INSERT INTO #AlterStatements
					SELECT ''IF NOT EXISTS(SELECT 1 FROM '+@SyncToDB+'.SYS.OBJECTS WHERE NAME  = ''''''+Constraint_name+'''''')  BEGIN  ALTER TABLE '+@SyncToDB+'.['' +Referencing_Schema_name+''].[''+Referencing_Object_name+'']  WITH CHECK ADD  CONSTRAINT [''+Constraint_name+''] FOREIGN KEY( [''+Referencing_Column_Name
					+'']) REFERENCES [''+Referenced_Schema_name+''].[''+Referenced_Object_name+''] ([''+Referenced_Column_Name+''])  
					ALTER TABLE '+@SyncToDB+'.[''+Referencing_Schema_name+''].[''+Referencing_Object_name+ '']  CHECK CONSTRAINT [''+Constraint_name +'']   END 
					
					ELSE 
					BEGIN
					 ALTER TABLE '+@SyncToDB+'.['' +Referencing_Schema_name+''].[''+Referencing_Object_name+'']  WITH CHECK ADD  CONSTRAINT [''+Constraint_name+''_1] FOREIGN KEY( [''+Referencing_Column_Name
					+'']) REFERENCES [''+Referenced_Schema_name+''].[''+Referenced_Object_name+''] ([''+Referenced_Column_Name+''])  
					ALTER TABLE '+@SyncToDB+'.[''+Referencing_Schema_name+''].[''+Referencing_Object_name+ '']  CHECK CONSTRAINT [''+Constraint_name +''_1]   END 
					
					''

					FROM 
					(
					SELECT 
					S1.NAME as Referencing_Schema_name
					,o1.name as Referencing_Object_name
					, c1.name as referencing_column_Name
					,S2.NAME as Referenced_Schema_name
					, o2.name as Referenced_Object_name
					, c2.name as Referenced_Column_Name
					, s.name as Constraint_name
					from '+@SyncFromDB+'..sysforeignkeys fk
					inner join '+@SyncFromDB+'..sysobjects o1 on fk.fkeyid = o1.id
					inner join '+@SyncFromDB+'..sysobjects o2 on fk.rkeyid = o2.id
					inner join '+@SyncFromDB+'..syscolumns c1 on c1.id = o1.id and c1.colid = fk.fkey
					inner join '+@SyncFromDB+'..syscolumns c2 on c2.id = o2.id and c2.colid = fk.rkey
					inner join '+@SyncFromDB+'..sysobjects s on fk.constid = s.id
					inner join '+@SyncFromDB+'.sys.tables t1 on t1.object_id=c1.id
					inner join '+@SyncFromDB+'.sys.tables t2 on t2.object_id=c2.id
					INNER JOIN '+@SyncFromDB+'.SYS.schemas S1 ON T1.SCHEMA_ID=S1.SCHEMA_ID
					INNER JOIN '+@SyncFromDB+'.SYS.schemas S2 ON T2.SCHEMA_ID=S2.SCHEMA_ID
					)MASTERDB
							WHERE NOT EXISTS
											(
											
											SELECT * FROM
											(SELECT 
												S1.NAME as Referencing_Schema_name
												,o1.name as Referencing_Object_name
												, c1.name as referencing_column_Name
												,S2.NAME as Referenced_Schema_name
												, o2.name as Referenced_Object_name
												, c2.name as Referenced_Column_Name
												, s.name as Constraint_name
												from '+@SyncToDB+'..sysforeignkeys fk
												inner join '+@SyncToDB+'..sysobjects o1 on fk.fkeyid = o1.id
												inner join '+@SyncToDB+'..sysobjects o2 on fk.rkeyid = o2.id
												inner join '+@SyncToDB+'..syscolumns c1 on c1.id = o1.id and c1.colid = fk.fkey
												inner join '+@SyncToDB+'..syscolumns c2 on c2.id = o2.id and c2.colid = fk.rkey
												inner join '+@SyncToDB+'..sysobjects s on fk.constid = s.id
												inner join '+@SyncToDB+'.sys.tables t1 on t1.object_id=c1.id
												inner join '+@SyncToDB+'.sys.tables t2 on t2.object_id=c2.id
												INNER JOIN '+@SyncToDB+'.SYS.schemas S1 ON T1.SCHEMA_ID=S1.SCHEMA_ID
												INNER JOIN '+@SyncToDB+'.SYS.schemas S2 ON T2.SCHEMA_ID=S2.SCHEMA_ID
												) SlaveDB
												WHERE SlaveDB.Referencing_Schema_name=MASTERDB.Referencing_Schema_name
												  AND SlaveDB.Referencing_Object_name=MASTERDB.Referencing_Object_name
												  AND SlaveDB.referencing_column_Name=MASTERDB.referencing_column_Name
												  AND SlaveDB.Referenced_Schema_name=MASTERDB.Referenced_Schema_name
												  AND SlaveDB.Referenced_Object_name=MASTERDB.Referenced_Object_name
												 -- AND Constraint_name=Constraint_name					  
											)
					ORDER BY MASTERDB.Referencing_Object_name
				')

 	
			----CURSOR TO EXECUTE/PRINT EACH STATEMENT SEPARATELY-----
		DECLARE MY_CURSOR CURSOR READ_ONLY 
		FOR 		
			SELECT TSQLStmt FROM #AlterStatements
			
			OPEN My_Cursor 
			DECLARE 	@SQLstmt VARCHAR(MAX)

			Fetch NEXT FROM MY_Cursor INTO @SQLstmt
			While (@@FETCH_STATUS <> -1)
			BEGIN

				EXEC (@SQLstmt)
			--	PRINT (@SQLstmt)
			FETCH NEXT FROM MY_CURSOR INTO @SQLstmt
			END
			CLOSE MY_CURSOR
			DEALLOCATE MY_CURSOR
			-----
					
			
DROP TABLE #AlterStatements 		
 END