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initializing and referencing collectionsuntil you initialize a collection a nested table or varray is automatically null ie the collection itself is
defining and declaring collectionsto create the collections you must define a collection type and then declare the collections of that type you can
varrays versus nested tablesthe nested tables are differing from varrays in the following ways1 varrays have a maximum size while nested tables
nested tables versus index-by tablesthe index-by tables and nested tables are just similar for eg they have similar structure and their
what is a collectionthe collection is an ordered group of elements all of similar type for eg the grades for a class of students each element has a
null statementthe null statement clearly specifies in action it does nothing other than to pass control to the next statement it can though improve
goto statementthe goto statement branches to a label unconditionally the label must be exclusive within its scope and should precede an executable
sequential controldissimilar to the if and loop statements the goto and null statements are not important to the plsql programming the configuration
dynamic rangesthe plsql lets you determine the loop range dynamically at run time as the example below showsselect countempno into empcount from
iteration schemesthe bounds of a loop range can be variables literals variables or expressions but must compute to integers below are some of the
for-loopwhile the number of iterations through a while loop is unknown till the loop completes then the number of iterations through a for loop is
while-loopthe while-loop statement relates a condition with the series of statements enclosed by the keywords loop and end loop as shownwhile
loop labelslike the plsql blocks loops can also be labeled the label an undeclared identifier enclosed by double angle brackets should appear at the
exit-whenthe exit-when statement permits a loop to complete conditionally whenever the exit statement is encountered the condition in the when clause
exitthe exit statement forces a loop to done unconditionally whenever an exit statement is encountered the loop is done immediately and controls the
iterative control loop statementsthe loop statement executes a series of statements multiple times there are 3 forms of loop statements loop
plsql conditional control if statementsfrequently it is necessary to take the alternative actions depending on the circumstances the if statement
in operatorthe operator in tests the set membership this means equal to any member of the set may have nulls but they are ignored for illustration
between operatorthe operator between tests whether the value lies in a specified series that means greater than or equivalent to low value and less
like operatoryou use the like operator to compare the character value to a pattern the case is significant like returns the boolean value true when
is null operatorthe is null operator returns the boolean value true whenever its operand is null or false if it is not null the comparisons including
comparison operatorsthe comparison operators can compare one expression to another the outcome is always true false or null usually you use a
short-circuit evaluation when computing a logical expression the plsql uses short-circuit evaluation that is the plsql stops computing the expression
order of evaluationwhen you do not use the parentheses to specify the order of evaluation the operator precedence determine the order now compare the
plsql expressions the expressions are constructed by using the operands and operators an operand is a constant literal variable or function call