SELECT @pk_2 = 'AND ' + @local_schema_name + '_TARGET.' + column_name + ' = ' + @local_schema_name + '_SOURCE.' + column_name 
FROM @pk_table WHERE key_seq = 2

SET @pk_2 = '';
SELECT @pk_2 = @pk_2 + ' AND ' + @local_schema_name + '_TARGET.' + column_name + ' = ' + @local_schema_name + '_SOURCE.' + column_name  
FROM @pk_table WHERE key_seq > 1;