Identify Cardinality

Do anyone know how i can identify relationship verbs or cardinality marks in my ERD?

PK food_category_code

PK animal_breed_code

PK animal_breed_code
PK food_item_id
FK Daily_requirement

PK food_item_id
PK food_category_code
FK Food_item_description

PK animal_id
PK checkup_date

PK animal_id

PK animal_id
PK food_item_id
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You can't.  The Relationships window in Access is not really an ERD (Entity Relationship Diagram).  It shows tables and foreign key constraints, which is not quite the same thing.  A foreign key does not express cardinality, except for designating which table is the "many" side (if you can call that expressing cardinality).  Of course, the "many" side is quite evident in both the Relationship window and the query designer window in Access.

To depict cardinality, optionality, relationship names, role names and other logical constructs you need a different tool. Good tools are quite pricey, but for something economical, you might want to have a look at Visio professional.
DatabaseMX (Joe Anderson - Microsoft Access MVP)Database Architect / Systems AnalystCommented:

Cool post !  :-)

shorisAuthor Commented:
Ok.. that makes sense but how would i should in Visio the cardinality from the above tables? maybe i'm just confused of cardinality..
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Jim Dettman (Microsoft MVP/ EE MVE)President / OwnerCommented:
<<maybe i'm just confused of cardinality>>

   Cardinality is the measure of how unique the data is or in other words, how many different members there are in a set.

  Typically you talk about cardinality in when working with indexes.  For example, if you have a yes/no column, it generally makes a poor choice for an index because there are only two possible values to the data.  Indexing doesn’t make sense because you’ll end up doing a table scan anyway.

    Usually, it’s expressed as a percentage.

shorisAuthor Commented:
Ok that makes sense.. thanks Jdettman, but in my tables above what would be cardinality?
shorisAuthor Commented:
Based on my tables, can anyone understand the relationships?
Jim Dettman (Microsoft MVP/ EE MVE)President / OwnerCommented:
<<Ok that makes sense.. thanks Jdettman, but in my tables above what would be cardinality?>>

  You can't answer that until the tables have data.  The question you need to answer is "How unique is the data in the column?"

   An autonumber column would have a high cardinality; every row would have a unique value
   A column with a customer name would be fairly unique (lot's of different names, but there could be quite a few Smiths)
   A yes/no column has a very low cardinality; there are only two possible values that would appear in the column.

<<Based on my tables, can anyone understand the relationships?>>



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OK, there is some confusion here about different uses of the term "cardinality".  Since you mentioned ERD's and relationships, I gave the answer in that context. The realtionship cardinality is often depicted in an ERD and indicates how many entities may participate on each side of the relationship.  Examples are 1:1 (one-to-one), 1:M (one-to-many), 0:M, M:M and so forth.  That information is usually conveyed in the sybology of the particular diagramming technique.  

Row cardinality refers to the number of rows in a table,  but is NEVER shown in an ERD.  Column cardinality refers to the diversity of values in a column. While very important to index choice, and is not relevant to an ERD, either.
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