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8 Cards in this Set
- Front
- Back
Data Integrity |
Entity Integrity Refferencial Integrity Domain Integrity |
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Entity integrity |
Every table needs primary key Unique Not null (NN) Never change |
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Primary key |
Surrogot - computed generated no meaning Natural - username, email, other unique values Unique Not null Never changes |
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Referential integrity |
Foreign keys referencing other columns Gotta tell database it's a foreign key FK When reference can be trusted! |
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Domain integrity |
Proper data in column. Ensure data is what is expected. Domain expreses what is allowed and what is not allowed. Fit within the rules. Data type, string, number Not null Unique |
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1NF |
Make sure everything is atomic Singular names in columns Every column describes table name |
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2NF |
In conjoined table, dont have information that is not relevant or is only relevant to 1 of the columns It should reference both columns User_items should have user_id Item_id If everyone has the same number of the item, then item_number is a partial dependent because it refers only to the item_id, and should be in the items table If everyone has different numbers of an different items then it can be in the same table, because it matter WHICH user HAS 3 of THIS CERTAIN item |
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3NF |
Transitive dependency is like Listing_id | $ | Catagory | Catag Des The category description can change with the listing ID, unlike something like most popular item of the day, but it is solely dependent upon category in reality Break it off into it's own table Catagory_id | Cat.. | Cat.. description Now it has it's own ID. Replace the catagory up above with catagory_ID reference and remove the catagory description from the table |