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Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
Cis245 Midterm Review
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Cis245 Midterm Review

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  • 1. CIS245
  • 2.  Primary key Composite key/multiple-field primary key Foreign key One-to-one relationship One-to-many relationship Many-to-many relationship Referential Integrity
  • 3.  Have more than one table where tables are related to each other  One to one  One to many  Many to manyA combination of fields may be used for the table‟s primary key
  • 4.  Each table contains data about a specific subject (customers, loans) Each table on the „one‟ side has a primary key Primary key of the “one” table is a foreign key in the many table
  • 5.  Twotables are related, but can have many records in each table in common  One student can attend many courses; one course can be attended by many students Implement a many to many relationship by creating a pair of one to many relationships with a third table  Third table is often referred to as a “join” or “junction” table
  • 6. A foreign key points to a record in another table Foreign key “looks like” the related primary key  Same number of fields  Data types for each field must match  Field names don‟t matter
  • 7.  Makessure that the records in related tables are consistent  Must have a customer in the customer table for an order assigned to that customer  Avoids “orphans” Cannotdelete a record or change the primary key in the one table when associated records are in the many table, unless have cascade delete and cascade update enabled
  • 8.  Data constraints: What is “good” data?  Valid type of data  Valid values for the data  Many can be enforced through the design of the Access tables and relationships
  • 9.  Validation rule: Condition that the corresponding field must satisfy Validation text: Displayed if the condition of validation rule is not satisfied Table Properties validation rule: Required when a constraint requires a comparison of the contents of two or more fields in the same table
  • 10.  Maintains a sorted list of the current values of a field or fields Items in the list point to the records that have the identified value Created automatically for primary keys
  • 11.  Normalization is a process Goals:  Reduce space required to store data by eliminating duplicate data in database  Reduce inconsistent data in database by storing data only once  Reduce chance anomalies
  • 12.  Deletion anomaly  User deletes data from database  Unintentionally deletes only occurrence of data in database Update anomaly  Due to redundant data in database  User fails to update some records or updates records erroneously Insertion anomaly  User cannot add data to database unless preceded by entry of other data
  • 13.  Dependency: Column value depends on value in a different column  Functional dependency: values explicitly one to one  Partial dependency: Column value dependent on only part of primary/candidate key
  • 14.  Determinant: Field or collection of fields whose value determines value in another field Inverse of dependency  Department is a determinant
  • 15.  Retrieve data from other tables or queries Field names appear in the Field row of the grid Criteria row of grid  Limits the displayed rows to those that meet a specified condition  Contains any statement that evaluates to True or False
  • 16.  Inner join  Default join type  Includes rows only when the fields being compared contain matching values Outer join  Includes all rows from one table and data from second table where there is a match
  • 17.  Use when selecting records from one table, but need to limit the records returned by a value in another table Use the „In‟ comparison  Sub-query can return only a single field Sub-query must run before the main query  Use parentheses to control order of execution
  • 18.  Select queries that aggregate values The Group By item in the Total list box tells Access to aggregate the other fields per each unique value within the Group By field A field that‟s part of the aggregate uses Having instead of Where
  • 19.  Delete queries: Remove rows from a table Make-table queries: Query results are stored in a new table Append queries: Query results of the are appended (added) to an existing Access table Update queries: Change field values in existing rows in a table
  • 20.  Parameter queries use placeholder to substitute for the constant values placed in the query grid Allow changes to criteria “on the fly” when the query is run

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