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

Built-in functions-comparison operators, Built-In Functions The PL/SQL p...

Built-In Functions The PL/SQL provides a lot of powerful functions to help you to manipulate the data. These built-in functions fall into the categories as shown below: error r

Parameter and keyword description - %type attribute, Parameter and Keyword ...

Parameter and Keyword Description: collection_name: This keyword identifies the index-by table, nested table, or varray formerly declared within the present scope. cu

Parameter and keyword description - open-for statement, Parameter and Keywo...

Parameter and Keyword Description: cursor_variable_name: This identifies a cursor variable or the parameter formerly declared within the present scope. host_cursor_va

Assignment of DBMS in SQL server, i have an assignment of DBMS subject, thi...

i have an assignment of DBMS subject, this assignment is based on SQL server and power BI

Mutual recursion, Mutual Recursion The Subprograms are mutually recursi...

Mutual Recursion The Subprograms are mutually recursive if they directly or indirectly call each other. In the illustration below, the Boolean functions odd & even, that dete

Calculate days between ordering and shipping, An analyst in the quality ass...

An analyst in the quality assurance office reviews the time lapse between receiving an order and shipping an order. Any orders that have not been shipped within a day of the order

Initializing objects in pl sql, Initializing Objects: Till you initiali...

Initializing Objects: Till you initialize an object by calling the constructor for its object type, the object is automatically null. That is, the object itself is null, not me

Fetching from a cursor variable, Fetching from a Cursor Variable The F...

Fetching from a Cursor Variable The FETCH statement retrieve rows one at a time from the product set of a multi-row query. The syntax for the same is as shown: FETCH {curso

Assignment source not a literal - variable, Assignment Source Not a Literal...

Assignment Source Not a Literal - Variable Syntax: SET SN = SID (SUBSTRING (SN.C FROM 1 FOR 1)||'5');

Pl/sql expressions , Pl/SQL Expressions The Expressions are constructed...

Pl/SQL Expressions The Expressions are constructed by using the operands and operators. An operand is a constant, literal, variable, or function call which contributes a value

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