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

Some varray examples-manipulating collections, Some Varray Examples In S...

Some Varray Examples In SQL Plus, assume that you define an object type Project, as described below: SQL> CREATE TYPE Project AS OBJECT ( 2 project_no NUMBER(2), 3 title VARCHA

produce vertical output format- oracle, Create a Oracle procedure to produ...

Create a Oracle procedure to produce vertical output format when selecting rows from a database table.

Biconditional - sql, Biconditional - SQL The biconditional p ↔ q can b...

Biconditional - SQL The biconditional p ↔ q can be expressed in Tutorial D by p = q and the same is true of SQL. The question then arises as to whether, in SQL, p = q is equiv

Package - pl/sql programming, What Is a Package? The package is a sch...

What Is a Package? The package is a schema object that group logically related PL/SQL items, types, and subprograms. The Packages usually have 2 parts, a specification & a bo

Adding table constraints, Adding Table Constraints ALTER TABLE ENROL...

Adding Table Constraints ALTER TABLE ENROLMENT ADD CONSTRAINT NameNotNull CHECK (Name IS NOT NULL) ; ALTER TABLE ENROLMENT ADD CONSTRAINT PK_StudentId_CourseId PRIM

Write a pl-sql program using the implicit cursor, Question: a) Given th...

Question: a) Given the following relation: Location(loc_id, bldg_code, room, capacity) The underlined field is a primary key. (i) Write a PL/SQL program using the impl

Map and order methods, Map and Order Methods: The values of the scalar...

Map and Order Methods: The values of the scalar datatype like CHAR or REAL have a predefined order that allows them to be compared. While, the instances of an object type has

Parameter & keyword description-execute immediate statement, Parameter and ...

Parameter and Keyword Description: dynamic_string: This is a string variable, literal, or expression which represents a SQL statement or the PL/SQL block. define_vari

Logical connectives - sql, Logical Connectives - SQL SQL's extended t...

Logical Connectives - SQL SQL's extended truth tables in which the symbol, for unknown, appears along with the usual T and F. Negation (NOT, ¬) Conjunction (

Sql queries-oracle , 1- You can check attribute names from each table in D...

1- You can check attribute names from each table in DBF11 by running for example:  desc dbf11.Member;  desc dbf11.Agent;  desc dbf11.Producer; Because some attribute names in

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