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In this module you learned about relational constructs (such as tables, rows, and columns) and how they are created.
You also learned the characteristics of tables, the rules for table columns and rows, and which data domains can be assigned to the
columns.
After learning the difference between null values, blanks, and zeros, you learned how to identify candidate and primary keys for
database tables.
Finally, you learned that enforcing referential integrity ensures that users won't inadvertently enter data that refers to
non-existent records in other tables.
Learning objectives
Now that you have completed the lessons in this module, you should be able to:
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List the steps in the database life cycle (DBLC)
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Explain why an ER diagram is translated into relational constructs
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Describe the characteristics of tables
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List the rules for table rows and columns
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Define data domains and identify the domains that support calculations
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Differentiate between nulls, blanks, and zeros
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Define and identify key columns and descriptor columns
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Define primary keys
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Define concatenated primary keys
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Describe all-key relations
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Identify foreign keys
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Define the concept of referential integrity
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attribute:
A characteristic of an entity; data that identifies or describes an entity. Usually represented as a column in a table, attributes store data values.
- base table:A table stored in a database.
- business objects:
Items in a business environment that are related, and about which data need to be stored (e.g., customers, products, orders, etc.).
- concatenated primary key: A primary key made up of more than one field.
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data type:
The category of data stored in a database. Each field in a database must have a data type assigned to it, such as Integer, Text, or Date/Time.
- descriptor column: A descriptor column contains a non-key attribute of an entity.
- domain: Determines the type of data values that are permitted for that attribute.
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Entity: A single stand-alone unit or a business object about which data are stored in a database; usually synonymous with a database table.
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entity-relationship (ER) diagram: A diagram used during the design phase of database development to illustrate
the organization of and relationships between data during database design.
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field: The smallest structure in a table; contains data describing the subject of a table.
- foreign key: A field (or combination of fields) used to link tables; a corresponding primary key field occurs in the same database.
- integer division: A mathematical operation that returns the integer portion of a division and discards the remainder.
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key column: A key column contains information that distinguishes that person, place, or thing from every other
item represented in the table.
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normalize
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null value
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one-to-many relationship
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primary key
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query
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record
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referential integrity
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relational database management system (RDBMS)
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relational notation
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relation
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relationship
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set theory
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Structured Query Language (SQL)
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table
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tuple
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user view
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Virtual table: A table stored in the computer’s memory. Virtual tables themselves are not stored in
the database; rather, the definition of the view is stored and given a name. Users call up that name, and the view is created (from
base tables) on the fly. When a user closes the view, the view disappears from memory and is recreated the next time
its name is invoked.
In the next module, database normalization and first, second, and third normal forms will be discussed.
Relational Constructs - Quiz
Before moving to the next module, click the Quiz link below to check your knowledge of relational constructs.
Relational Constructs - Quiz
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