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WHILE-LOOPThe WHILE-LOOP statement relates a condition with the series of statements enclosed by the keywords LOOP and END LOOP, as shown:WHILE condition LOOPsequence_of_statementsEND LOOP;Before each of the iteration of the loop, the condition is computed. If the condition is true, then the series of statements is executed, then the control resumes at the top of the loop. When the condition is false or null, the loop is then bypassed and control passes to the next statement. An illustration is shown below:WHILE total <= 25000 LOOP...SELECT sal INTO salary FROM emp WHERE...total := total + salary;END LOOP;The number of iterations depends on the condition and is not known until the loop done. The condition is tested at the top of the loop, so the series might execute zero times. In the last illustration, if the initial value of total is bigger than 25000, the condition is false and the loop is bypassed.A few languages have a LOOP UNTIL or REPEAT UNTIL structure, that tests the condition at the bottom of the loop rather than at the top. So, the sequence of the statements is executed at least once. The PL/SQL has no such structure, but you can easily build one, as shown:LOOPsequence_of_statementsEXIT WHEN boolean_expression;END LOOP;To make sure that a WHILE loop executes at least once, then use an initialized Boolean variable in the condition which is as shown below:done := FALSE;WHILE NOT done LOOPsequence_of_statementsdone := boolean_expression;END LOOP;The statement inside the loop should assign a new value to the Boolean variable. Or else, you have an infinite loop. For illustration, the following LOOP statements are logically equal:WHILE TRUE LOOP | LOOP... | ...END LOOP; | END LOOP;
which operation is used if we are interested in only certain columns of a table?
Example of ADD CONSTRAINT in SQL Example: Alternative formulation for MAX_ENROLMENTS ALTER TABLE IS_ENROLLED_ON ADD CONSTRAINT MAX_ENROLMENTS CHECK ((SELECT COUNT (*)
Updating a Variable Assignment of an attribute value in a variable of a structured type Synatx: SET SN.C = 'S2'; As in Example the entire statement is equivalent to a
write the program for traffic control system with 10 second, 15 secod, and 20 second delay
Find the account numbers of all customers whose balance is more than 10,000 $
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
Cursors To execute the multi-row query, the Oracle opens an unnamed work region which stores the processing information. The cursor names the work region, access the informa
Description: Demonstrate your knowledge of PL/SQL programming by writing and thoroughly testing triggers and stored procedures associated with an e-commerce application that pr
Datatype Conversion At times it is necessary to convert a value from one datatype to another. For e.g. if you want to inspect a rowid, you should convert it to a character stri
Package Body: The package specification is implemented by the package body. That is, the package body has the definition of every cursor and the subprogram declared in the pac
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