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WHEN or THEN Key Constraints
Suppose a table has two columns representing a period of time throughout which the information conveyed by the other columns is recorded as having been the case. A salary history table for employees, with columns From and To for dates defining the applicable time periods, would be a good example.
A constraint is needed to avoid the possibility of an employee being shown as having two different salaries on the same day, which could happen if two rows for the same employee have overlapping periods indicated by their From and To dates. The term "WHEN/THEN constraint" appeals to the notion of "unpacking" the table so that each row is replaced by one or more rows, one for each date contained in its from-to period: when the relation is unpacked, then the given key constraint (e.g., on employee number and date) is to hold.
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The accuracy of product table data is critical and the Brwebean's. owner wants to have an audit file that contains information regarding all DML activity on the BB_PRODUCT table. T
Remote Operations: As the illustration shows below, the PL/SQL subprograms can execute the dynamic SQL statements which refer to the objects on a remote database: PROCEDURE
Expression: This is a randomly complex combination of constants, variables, literals, operators, & function calls. The simplest expression consists of a single variable. If th
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Package Specification The package specifications contain the public declarations. The scopes of these declarations are local to your database representation and global to the
Find the account numbers of all customers whose balance is more than 10,000 $
i NEED THE QURIES TO SOME OF THE PROBLEMS USING plsql
Using DELETE This process has three forms. The DELETE removes all elements from the collection. DELETE(n) removes the nth element from the nested table. When n is null, then D
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