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

Operators on tables and rows, Operators on Tables and Rows Row Extrac...

Operators on Tables and Rows Row Extraction TUPLE FROM r, SQL has row subqueries. These are just like scalar subqueries except that they may specify more than one column.

Definition of cross join - sql, Definition of CROSS JOIN - SQL Let s ...

Definition of CROSS JOIN - SQL Let s = t1 CROSS JOIN t2, where t1 and t2 are table expressions optionally accompanied by range variables. Then: Note: Here T denotes Table

Ensuring backward compatibility, Ensuring Backward Compatibility   The...

Ensuring Backward Compatibility   The PL/SQL Version 2 permits some abnormal behavior which Version 8 disallows. Particularly, Version 2 permits you to (i) Make the forw

Error handling in pl/sql, Error Handling The PL/SQL makes it easy to de...

Error Handling The PL/SQL makes it easy to detect and process the predefined and user-defined error conditions known as exceptions. Whenever an error occurs, an exception is ra

Stored subprograms, Stored Subprograms Normally, tools (like Oracle Fo...

Stored Subprograms Normally, tools (like Oracle Forms) which incorporate the PL/SQL engine can store subprograms locally for later, strictly local execution. Though, to become

Bulk fetching - bulk bind performance improvement, Bulk Fetching The i...

Bulk Fetching The illustration below shows that you can bulk-fetch from a cursor into one or more collections: DECLARE TYPE NameTab IS TABLE OF emp.ename%TYPE; TYPE S

Example of table literal - sql, Example of Table Literal - SQL Exampl...

Example of Table Literal - SQL Example: A Table Literal (correct version) VALUES ('S1', 'C1', 'Anne'), ('S1', 'C2', 'Anne'), ('S2', 'C1', 'Boris'), ('S3', 'C3'

Example of not exists operator - sql, Example of NOT EXISTS Operator - SQL ...

Example of NOT EXISTS Operator - SQL Example is a translation into SQL of the corresponding example, which is included there merely to show that for any scalar comparison the

Creating a table, Creating a Table Syantax: CREATE TABLE ENROL...

Creating a Table Syantax: CREATE TABLE ENROLMENT (StudentId SID, Name   VARCHAR (30) NOT NULL, CourseId CID, PRIMARY KEY (StudentId, CourseId)) ; Explan

Declaring subprograms, Declaring Subprograms   You can declare subprog...

Declaring Subprograms   You can declare subprograms in any PL/SQL subprogram, block, or package. But, you should declare subprograms at the end of the declarative part after a

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