Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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).
Blocks: The fundamental program unit in the PL/SQL is the block. The PL/SQL block is defined by the keywords BEGIN, DECLARE, EXCEPTION, and END. These keywords partition the b
Example of Check Constraints Example: Workaround for when subqueries not permitted in CHECK constraints CREATE FUNCTION NO_MORE_THAN_20000_ENROLMENTS ( ) RETURNS BOOLEAN
%ROWTYPE: This attribute gives a record type which represents a row in the database table or a row fetched from a formerly declared cursor. The Fields in the record and corresp
Question 1. Update stock levels when the order is cancelled At times, customers make mistakes in submitting their orders and call to cancel the order. Brewbean’s wants to create a
Type versus Representation Confusion in SQL This describes how a value might have two or more distinct representations. For example, user-defined type POINT might have a decla
COMMIT Statement The COMMIT statement explicitly makes everlasting changes to the database during the present transaction. The Changes made to the database are not considered e
Inner Join We have learned how to retrieve data from one table by using SELECT statement. But, as we have learned, normalized relational databases mean the data is spread betw
ALTER TABLE bb_basketitem ADD CONSTRAINT bitems_qty_ck CHECK (quantity BEGIN INSERT INTO bb_basketitem VALUES (88,8,10.8,21,16,2,3); END; Brewbean’s wants to add a check
Scoping Within the similar scope, all the declared identifiers should be unique. So, even if their datatypes differ, the variables and parameters cannot share the similar name.
Effects of NULL for union - SQL The treatment of NULL in invocations of EXCEPT is as for UNION. This is different from its treatment in those of NOT IN and quantified compari
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!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd