Example of when or then constraints - sql, PL-SQL Programming

Assignment Help:

Example of WHEN or THEN Constraints

A concrete example showing how SQL supports WHEN/THEN constraints

CREATE TABLE SAL_HISTORY (EmpNo CHAR (6),

Salary INTEGER NOT NULL,

From DATE

To DATE

PERIOD FOR During (From, To),

PRIMARY KEY (EmpNo, During WITHOUT OVERLAPS)

) ;

The PERIOD FOR specification states that the From and To values in each row denote a time interval (called a period because SQL uses the term "interval" for something else). The From values are treated as closed bounds, the To values as open bounds, so a given row in SAL_HISTORY indicates that an employee was paid a certain salary from the given From date up to but not including the given To date. The specification implies the column constraint NOT NULL NOT DEFERRABLE ENFORCED for each of columns From and To. During WITHOUT OVERLAPS, which, if required, must appear as the last element of the key, specifies that if the same EmpNo value appears in two distinct rows of SAL_HISTORY, then the From and To values in those rows must denote During periods that do not overlap (have no date in common).


Related Discussions:- Example of when or then constraints - sql

Manipulating individual elements - pl/sql, Manipulating Individual Elements...

Manipulating Individual Elements Faraway you have manipulated an entire collection. Within the SQL, to manipulate the individual elements of the collection, and then use the ope

Records - syntax, Records Records are the items of the type RECORD. The...

Records Records are the items of the type RECORD. The Records have exclusively named fields that can store the data values of various types. And hence, a record treat associate

Assignment2, How do I display usernames for students from a student table, ...

How do I display usernames for students from a student table, assigning each student a username initials001 (initials is the actual student initials), and if the students initials

Row counterparts of table operators - sql, Row Counterparts of Table Operat...

Row Counterparts of Table Operators SQL does not have counterparts tuple rename, tuple projection, tuple extension, tuple join and tuple compose. To obtain the same effects as

If statement - syntax, IF Statement The IF statement executes a series ...

IF Statement The IF statement executes a series of statement conditionally. Whether the series is executed or not depends on the value of the Boolean expression. Syntax:

Components of an object type - attributes in pl/sql, Attributes: Just ...

Attributes: Just similar to variable, an attribute is declared with a name and datatype. The name should be exclusive within the object type. The datatype can be any Oracle ty

Advantages of invoker rights, Advantages of Invoker Rights The Invoker-...

Advantages of Invoker Rights The Invoker-rights routines centralize the data retrieval. They are particularly helpful in applications which store data in various schemas. In su

Design a script and integrate procedures, Initial thought process: Design...

Initial thought process: Design a script which was simple and user friendly. Integrate procedures/functions to extract data under the hood. I focused on giving the user the opt

Using delete - collection method, Using DELETE This process has three ...

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

Explicit cursors, Explicit Cursors The set of rows returned by the que...

Explicit Cursors The set of rows returned by the query can include zero, one, or multiple rows, depending on how many rows meet your search criteria. Whenever a query returns

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd