Unanswered: understanding relationships in database
I have just received a database (from which I need to extract selected data and import into mine). It appears to consist of 3 databases linked together: one just has forms (data entry database), the second tables which contain the data and then a database just for lookup tables.
The part of the database I am interested in (and confused about!), is the database which actually contains the data.
The thing is, None of the tables have any fields with unique id's (though there are fields which are specified as primary keys) - there are no relationships defined between any of the tables in the relationship window.
All I have to go on to put together queries it a data model diagram. I feel there is something I am not getting - as this database was designed by people with more expertise than me in this area. Could someone please help me understand how you can design a database with no unique ids.
i need to put together queries, but the relationships between the tables are a mystery to me. (it is my understanding that relationships work by matching data in key fields)
I can post the database to take a look at if needed.
you dont have to have ID's to make a relationship. You do need a logical connection between the tables. IE two tables one a teacher table another a schedual table. If both tables have teacher name in them then you can join the two tables. You dont need to have a teacher ID or anything of that nature. True it is best practice to have numeric ID's for speed and performance but you dont have to have it. My sugestion is for you to look at the design of the querys and see how they are joined. you should be able to defer the table realationships that way.