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

Magento change address format depending on store, Magento change address fo...

Magento change address format depending on store Project Description: What I need is that depending on the store in which the customer bought the address should change the fo

%notfound - implicit cursor attributes, %NOTFOUND The %NOTFOUND is the...

%NOTFOUND The %NOTFOUND is the logical opposite of the %FOUND. The %NOTFOUND yields TRUE when an INSERT, UPDATE, or DELETE statement affected no rows, or the SELECT INTO state

Currval and nextval - sql pseudocolumns, CURRVAL and NEXTVAL The serie...

CURRVAL and NEXTVAL The series is a schema object which generates the sequential numbers. Whenever you form a sequence, you can specify its primary value and an increment. T

Table comparison - sql, Table Comparison - SQL The following definitio...

Table Comparison - SQL The following definitions for relation comparisons: Let r1 and r2 be relations having the same heading. Then: r1 ⊆ r2 is true if every tuple of r1

Named notation, Named Notation The second procedure call uses the name...

Named Notation The second procedure call uses the named notation. An arrow (=>) serve as the relationship operator that associates the formal parameter to the left of the arro

Create Tables, Hi there, I have the final part of a submission to do, it ...

Hi there, I have the final part of a submission to do, it is a demonstration that takes place tomorrow. I do not have to use previous information, but i have resources that sho

In packages - subprograms, In Packages The Forward declarations also g...

In Packages The Forward declarations also group logically related subprograms in the package. The subprogram specifications go in the package specification, & the subprogram b

Group and having query, Using a join on 2 tables, select all columns and 10...

Using a join on 2 tables, select all columns and 10 rows from the 2 tables without the use of a Cartesian product. Query: SELECT * FROM EMPLOYEE1 E JOIN STAFF S ON E.EMP_

Package specification, The Package Specification The package specificat...

The Package Specification The package specifications contain the public declarations. The scopes of these declarations are local to your database representation and global to t

Join and and in sql, JOIN and AND in SQL In this Section is all about ...

JOIN and AND in SQL In this Section is all about one operator, JOIN. SQL's closest counterpart, NATURAL JOIN, has already been covered. Here we look at several other "join" op

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