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SQL Set Operators

SQL Set Operators   Traditional Set Operators: Union Compatibility:     Requirement for the traditional set operators.    Strong requirement.                         - Same number of columns.                         - Each corresponding column is compatible.                         - Positional correspondence.     Apply to similar tables by removing columns first. SQL UNION Example:           Example 1: Retrieve basic data about all university people.                     SELECT FacNo AS PerNo, FacFirstName                                      ...
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Integrity Rules

Integrity Rules

     Null value: 

      

        •Absence of a value (missing value)

        •Actual value unknown or not applicable for a row.

 

     Primary key (PK):

•column or combination of columns with unique values in each row
•No extraneous columns (minimal).

Foreign key (FK):

•column or combination of columns.
•Related to a primary key in a related table.
•Same data type and often same name as related PK.

Integrity Rules

•Entity Integrity:

 
        •Primary key for each table.
        •No missing (null) values for primary keys.
        •Ensures traceable entities.


    •Referential Integrity:

            •Two kinds of values for a foreign key in a row.
        •Match a primary key value of a related table (usual).
        •Null value (unusual).
        •Ensures valid references among tables.


Integrity Rule Violations:


Oracle Relational Diagram:







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SQL Set Operators

SQL Set Operators   Traditional Set Operators: Union Compatibility:     Requirement for the traditional set operators.    Strong requirement.                         - Same number of columns.                         - Each corresponding column is compatible.                         - Positional correspondence.     Apply to similar tables by removing columns first. SQL UNION Example:           Example 1: Retrieve basic data about all university people.                     SELECT FacNo AS PerNo, FacFirstName                                      ...
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