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Unformatted text preview: Cardinality: whatd the biggest number We show primary keys: UNDERLINED We show foreign keys: [BRACKETS] o Example: Invoices(Invoice # , Date, [Customer #] Hierarchical block handler: first database available o It could only deal with 1:1 and 1:M relationship (parent-child) o Single root entry point. You could only enter at one point o Explicit Pointer- helps to navigate you around a database Network: another database Ted Cod: try to design a better database o Based on relations (simple chunks of data) Consists of ruples(rows) and attributes (columns) Relationship between tables is done implicitly. We look at the data to see which ones match up For a long time relational databases were just a good idea Relation names must be unique Every relation must have a primary key Duplicate rows and columns are not allowed...
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- Spring '11