kieransgirl
Member
- Joined
- Oct 13, 2003
- Messages
- 59
can anyone describe the types of relationships to me in laymans terms? one to many, one to one, many to many...
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relationships- in databases... (1 Viewer)
- Thread starter kieransgirl
- Start date
Viper
Member
Well, let me see if i can put it in laymans terms... (i can do when making a database, but its hard to explain....)
One to One:
If one field can have only one unique value (like in a primary ID), and it can only correspond to another unique value, the relationship must be One-to-One.... You get me?
Eg. "Client_ID" related to "Stock_ID".
There can be only one client allocated to each client ID. The same applies for Stock ID.
One-To-Many:
If One unique value can somehow relate to a value that could be multiple values, the relationship should be One-to-Many.
Eg. "Stock_ID" related to "Order_ID"
There can only be one piece of stock allocated to the stock ID, but there can be many pieces of stock related to one particular order... hmm getting confusing?
Many-To-Many:
If a field that can be one of many values relates to another field that can hold many values, the relationship should be Many-To-Many.
Eg. "Order_ID" related to "Payment_ID"
Many orders can be related to many payments (like if the payments are made in installments...)
Im sorry i couldnt make it clearer... It'd be much easier to explain with a schema..
I hope this helps you
Cheers
One to One:
If one field can have only one unique value (like in a primary ID), and it can only correspond to another unique value, the relationship must be One-to-One.... You get me?
Eg. "Client_ID" related to "Stock_ID".
There can be only one client allocated to each client ID. The same applies for Stock ID.
One-To-Many:
If One unique value can somehow relate to a value that could be multiple values, the relationship should be One-to-Many.
Eg. "Stock_ID" related to "Order_ID"
There can only be one piece of stock allocated to the stock ID, but there can be many pieces of stock related to one particular order... hmm getting confusing?
Many-To-Many:
If a field that can be one of many values relates to another field that can hold many values, the relationship should be Many-To-Many.
Eg. "Order_ID" related to "Payment_ID"
Many orders can be related to many payments (like if the payments are made in installments...)
Im sorry i couldnt make it clearer... It'd be much easier to explain with a schema..
I hope this helps you
Cheers