control structures in pl/sql


Example 4-10 Basic LOOP Statement with EXIT WHEN Statement. In case of condition evaluates to then, SQL will execute . Let's take an example to see the whole concept: After the execution of the above code in SQL prompt, you will get the following result: JavaTpoint offers too many high quality services. Finally, the form of sequence processes the statements one by one in the order they are present. In Example 4-35, the NULL statement lets you compile this subprogram and fill in the real body later. When EXIT is found in the loop, the loop breaks and program flow moves to the next block of code. Example 4-14 CONTINUE WHEN Statement in Basic LOOP Statement. Mail us on [emailprotected], to get more information about given services. To simulate the STEP clause in PL/SQL, multiply each reference to the loop index by the desired increment. CASE STATEMENT is more efficient and less lengthy compared to IF statements. When executed, the GOTO statement transfers control to the labeled statement or block. The controller will exit from the IF-statement in the following two cases. Example 4-10 is logically equivalent to Example 4-9. else dbms_output.put_line('Failed'); The FOR-LOOP statement lets you specify a range of integers, then run a sequence of statements once for each integer in the range. Code line 5: Checking the condition 1, whether mark is greater or equal 70. Verifies if the value of the right operand is greater than left. Thus it is used while dealing with multiple mutually exclusive choices. LOOP statements; In Example 4-4, when the value of sales is larger than 50000, both the first and second conditions are true. In PL/SQL, we have the provision of labeling the loops which increases the readability and meaning of the code. If you want to exit the inner loop early but complete the current iteration of the outer loop, then label the outer loop and specify its name in the CONTINUE WHEN statement, as in Example 4-27. After each iteration, the program flow points back to the top of the loop until a certain condition is satisfied. Using a Simple IF-THEN Statement in PL/SQL. If lower_bound is greater than upper_bound, then the statements never run. Example 4-24 Specifying FOR LOOP Statement Bounds at Run Time. In Example 4-12, the outer loop is not labeled; therefore, the inner loop cannot transfer control to it. Cursors let you access data one row or one set of rows at a time. The WHILE-LOOP statement associates a condition with a sequence of statements. Code line 10: If a is greater than b, then condition in nested-if 1 will check if a is greater than c'(line 10). The inner loop references the index of the outer loop by qualifying the reference with the label of the outer loop. The control structures in PL/SQL consists of the program structures like the iteration, sequence, and selection. See "Using Numeric Functions" for information about SQL numeric functions. It is not a good programming technique to use GOTO statements because it reduces readability and traceability of code. The while loop executes commands in its body as long as the condtion remains true, find reverse of given number using while loop. Oracle provides the following types of decision making statements. The IF statement will consider the nearest END IF statement as an endpoint for that particular condition. Example 4-17 Simulating STEP Clause in FOR LOOP Statement, EXIT WHEN or CONTINUE WHEN Statement in FOR LOOP Statement, The index of a FOR LOOP statement is implicitly declared as a variable of type PLS_INTEGER that is local to the loop. WHEN condition_n THEN result_n If no condition is true, the CASE statement runs else_statements if they exist and raises the predefined exception CASE_NOT_FOUND otherwise. About us | Contact us | Advertise In Example 4-15, index is i, lower_bound is 1, and upper_bound is 3. PL/SQL has three categories of control statements: Conditional selection statements, which run different statements for different data values. END; WHILE [condition] when 'A' then dbms_output.put_line('Distinction'); The CASE statement is appropriate when a different action is to be taken for each alternative. Now suppose that the FOR LOOP statement that you must exit early is nested inside another FOR LOOP statement. In Example 4-18, the FOR LOOP statement tries to change the value of its index, causing an error. GOTO loopstart; The IF THEN statement has this structure: If the condition is true, the statements run; otherwise, the IF statement does nothing. END LOOP; i INTEGER := 1;

Also the increment value cannot be specified. As the condition becomes FALSE, the loop ends. dbms_output.put_line(k) The keyword loop has to be placed before the first statement in the sequence of statements to be repeated, while the keyword end loop is placed immediately after the last statement in the sequence. Known as logical AND. If no selector_value equals selector, the CASE statement runs else_statements if they exist and raises the predefined exception CASE_NOT_FOUND otherwise. The loop statements are: The statements that exit the current iteration of a loop are: EXIT, EXIT WHEN, CONTINUE, and CONTINUE WHEN and can appear anywhere inside a loop, but not outside a loop. The case statement evaluates a condition, and performs an action, such as an entire PL/SQL block, for each case. This syntax is used when you want to execute statements only when condition is TRUE. It is a basic conditional statement which will allow the ORACLE to execute/skip a particular piece of code based on the pre-defined conditions. The control statement is used to modify the flow of execution of the program. The GOTO statement changes the flow of control within a PL/SQL block. dbms_output.put_line(i); EXIT WHEN i>5; Else if condition2 fails, then C is greatest will be printed (line 13). PL/SQL Control Structures are used to control flow of execution. Searched, which evaluates multiple conditions and chooses the first one that is true. When none of the conditions satisfied, the then controller will execute ELSE block if present, then will exit from the IF-statement. In Example 4-10, the EXIT WHEN statement inside the basic LOOP statement transfers control to the end of the current loop when x is greater than 3. Code line 5: Checking the condition1, whether mark is greater or equal 70. After one iteration, the loop counter increases or decreases by one. END LOOP; The searched CASE statement has this structure: The searched CASE statement runs the first statements for which condition is true. END; I) GOTO label_name; They are used to repeat execution of one or more statements for defined number of times. The loop statement consists of WHILE LOOP, FOR LOOP, and basic LOOP. OReilly members experience live online training, plus books, videos, and digital content from nearly 200 publishers. In Example 4-1, the statements between THEN and END IF run if and only if the value of sales is greater than quota+200. The condition1 returns , then control will be executing and checks the condition2. Statement; DECLARE The For Loop variable is always incremented by 1. This is achieved with the help of LOOP statements. Copyright2005, 2006,Oracle. This is primarily used for initialization and declaration of the loop variables. Verifies if the value of the right operand is greater than equal to left. Example 4-13 CONTINUE Statement in Basic LOOP Statement. Code line 3: Declaring the variable b as NUMBER data type and initializing it with value 15. Code line 6: If 0, then a is even number will be printed. To prevent an infinite loop, a statement or raised exception must exit the loop. Both EXIT and CONTINUE have an optional WHEN clause, where you can specify a condition. PL/SQL supports the programming language features like conditional statements and iterative statements. In Example 4-19, a statement outside the FOR LOOP statement references the loop index, causing an error. <> If there is no ELSE block, and none of the condition satisfied, then the controller will skip all the action block and start executing the remaining part of the code. If the condition is true, the loop completes and control passes to the next statement. When the EXIT statement is encountered, the condition in the WHEN clause is evaluated. PLS-00103: Encountered the symbol "END" when expecting one of the following: PLS-00375: illegal GOTO statement; this GOTO cannot transfer control to label, -- (raises "unreachable code" if warnings enabled, Example 2-51, "Simple CASE Expression with WHEN NULL", Example 2-53, "Searched CASE Expression with WHEN IS NULL", "Query Result Set Processing With Cursor FOR LOOP Statements". In this example, we are going to print the greatest of three numbers by using Nested-If statement. Loop statements let you repeat behavior until conditions are met. To skip,/execute a particular code based on the condition. Example 4-3 Nested IF THEN ELSE Statements.

The EXIT statement transfers control to the end of a loop. dbms_output.put_line(i); The CASE statement has these forms: Simple, which evaluates a single expression and compares it to several potential values. Here we are going to see an example of Nested If , Example of Nested- If Statement: Greatest of three number. Q #5) What are the 6 relational operators? PL/SQL provides different kinds of statements to provide such type of procedural capabilities.These statements are almost same as that of provided by other languages. Note: Whenever condition evaluates to NULL, then SQL will treat NULL as FALSE. If the condition is true, the sequence of statements is executed, then control resumes at the top of the loop. The NESTED-IF statement is basically allowed programmers to place one or more IF condition inside another IF conditions other than normal statements. PL/SQL supports the following structures for iterative control: In simple loop, the key word loop should be placed before the first statement in the sequence and the keyword end loop should be written at the end of the sequence to end the loop. The below table lists down the operators from the high to low precedence. BEGIN -- Logically equivalent nested IF THEN ELSE statements, -- After EXIT statement, control resumes here, LOOP -- After CONTINUE statement, control resumes here, PLS-00363: expression 'I' cannot be used as an assignment target. EXIT; Example: Using a Simple IF-THEN Statement in PL/SQL shows a simple use of the IF-THEN statement. Example: Using a Simple IF-THEN Statement in PL/SQL, Example: Using the IF-THEN-ELSEIF Statement in PL/SQL, Example: Using the CASE-WHEN Statement in PL/SQL, Example: Using the IF-THEN_ELSE and CASE Statement in PL/SQL, Example: Using WHILE-LOOP for Control in PL/SQL, Example: Using the EXIT-WHEN Statement in PL/SQL, Example: Using the GOTO Statement in PL/SQL. After the FOR LOOP statement runs, the index is undefined. A block of code gets executed based on the condition. An EXIT WHEN statement in an inner loop can transfer control to an outer loop only if the outer loop is labeled. In the above syntax, keyword IF will be followed by a condition which evaluates to TRUE/FALSE. You can put the condition in an EXIT WHEN statement inside the FOR LOOP statement. Note: Whenever condition evaluated to NULL, then SQL will treat NULL as FALSE. Below table gives the summary of various conditional statements that we have discussed. Remaining conditions are not evaluated. In Example 4-25, the FOR LOOP statement executes 10 times unless the FETCH statement inside it fails to return a row, in which case it ends immediately. For clarity only, the inner loop also qualifies the reference to its own index with its own label. Verifies if an operand is equal to the value Null. Example 4-31 GOTO Statement Goes to Labeled NULL Statement. This type of loop allows the execution of a block of code to a particular number of times. END; FOR counter IN initial_value .. final_value LOOP The GOTO statement moves the control to a unique labeled block of code unconditionally. After each traversal, both the loops need to run successfully. END; DECLARE The numbers will be assigned in the declare part, as you can see in the code below, i.e Number= 10,15 and 20 and the maximum number will be fetched using nested-if statements. When a number can be divided into evenly (no remainder), then it is not a prime and the loop is immediately exited. Copyright - Guru99 2022 Privacy Policy|Affiliate Disclaimer|ToS, Introduction to Decision Making Statements, Oracle PL/SQL Package: Type, Specification, Body [Example], Oracle PL/SQL Trigger Tutorial: Instead of, Compound [Example], CASE Statement in Oracle PL/SQL with Examples, Top 65 PL/SQL Interview Questions & Answers (2022 Update). There should be an EXIT condition in the loop, otherwise the loop will get into an infinite number of iterations. Verifies if the value of the left operand is greater than right. Suppose that you must exit a FOR LOOP statement immediately if a certain condition arises. Code line 18: In case condition1 returns false, then condition in nested-if 2 will check if b is greater than c'(line 18). This syntax is used when you want to execute one set of statements when condition1 is TRUE or a different set of statements when condition2 is TRUE. Scripting on this page enhances content navigation, but does not change the content in any way. Each time control reaches the CONTINUE WHEN statement, the condition in its WHEN clause is evaluated. The CONTINUE statement exits the current iteration of a loop unconditionally and transfers control to the next iteration of either the current loop or an enclosing labeled loop. i := i+1; a := a + 1; When run, the GOTO statement transfers control to the labeled statement or block. The EXIT-WHEN statement lets you complete a loop if further processing is impossible or undesirable. Code line10: Printing the statement Program completed.

In Example 4-28, the statements in the first WHILE LOOP statement never run, and the statements in the second WHILE LOOP statement run once. Code line 21: If b is greater than c , then message B is greatest will be printed (line 19), else if condition2 fails, then C is greatest will be printed (line 21). For information about the PL/SQL exception-handling mechanism, see Chapter 11, "PL/SQL Error Handling.". #1) IF-THEN:This is one of the basic forms of IF statements. II) GOTO label_name; To choose among several values or courses of action, you can use CASE constructs. Code implementation with NESTED IF-THEN-ELSE: While implementing logic in PL/SQL, we may require to process a block of code repeatedly several times. In some languages, the FOR LOOP has a STEP clause that lets you specify a loop index increment other than 1. Example 1: In this example, we are going to print message whether the given number is odd or even. In Example 4-2, the statement between THEN and ELSE runs if and only if the value of sales is greater than quota+200; otherwise, the statement between ELSE and END IF runs. It gives the programmer a better control of preventing a particular code from executing (diagram 1) or choosing a desired code based on the condition (diagram 2). With REVERSE, the value of index starts at upper_bound and decreases by one with each iteration of the loop until it reaches lower_bound. when 'D' then dbms_output.put_line('Pass class'); Example 4-8 EXCEPTION Instead of ELSE Clause in CASE Statement. The GOTO statement, which goes to a specified statement, is seldom needed. A loop marks a sequence of statements that has to be repeated. Before each iteration of the loop, the condition is evaluated. #2) IF-THEN-ELSE:This is the next form of IF statement which has the ELSE keyword then the next block of code. In Example: Using the EXIT-WHEN Statement in PL/SQL, the loop completes when the value of total exceeds 25,000: The GOTO statement lets you branch to a label unconditionally; however, you would usually try to avoid exiting a loop in this manner.

dbms_output.put_line ('value of a: ' || a); #3) IF-THEN-ELSIF:This conditional statement gives the option of selecting among the alternatives. Using the IF-THEN_ELSE and CASE Statement in PL/SQL. The lower and upper bounds of a FOR LOOP statement can be either numeric literals, numeric variables, or numeric expressions. Once we encounter a true condition in one ELSIF block, other ELSE or ELSIFs will be ignored. This block of ELSE statements is optional and it executes when the condition is FALSE. grade char(1) := 'C'; It is iterated between the start and end integer values. when 'B' then dbms_output.put_line('First class'); PL/SQL condition and iterative structures have been explained in detail with examples here in this tutorial. For information about exceptions, see "Overview of Exception Handling".). Example 4-18 FOR LOOP Statement Tries to Change Index Value. In Example 4-22, the indexes of the nested FOR LOOP statements have the same name. Note that you do not have to declare or initialize the counter in the FOR-LOOP and any valid identifier can be used for the name, such as loop_counter. If, when you exit the inner loop early, you also want to exit the outer loop, then label the outer loop and specify its name in the EXIT WHEN statement, as in Example 4-26. Example 4-8 is logically equivalent to Example 4-7. > Using PL/SQL Example 4-6 uses a simple CASE statement to compare a single value to many possible values. The FOR LOOP statement in Example 4-16 is the reverse of the one in Example 4-15: It prints the numbers from 3 to 1. The FOR LOOP statement runs one or more statements while the loop index is in a specified range. The label can be placed at the end of the LOOP as well. Thus the code in the program does not run in sequence. This complex example combines the CASE expression with IF-THEN-ELSE statements. Code line 2: Declaring the variable a as NUMBER data type and initializing it with value 10. (For complete syntax, see "IF Statement".). Example 4-26 EXIT WHEN Statement in Inner FOR LOOP Statement, Example 4-27 CONTINUE WHEN Statement in Inner FOR LOOP Statement. In this chapter, we have learned the different decision-making statements and their syntax and examples. This syntax is used when you want to execute one set of statements when condition is TRUE or a different set of statements when condition is FALSE. The label can also be described for EXIT statements while coming out of the loop. END LOOP; DECLARE When possible, rewrite lengthy IF-THEN-ELSIF statements as CASE statements because the CASE statement is more readable and more efficient. while sql pl loop loops statement condition1 true end The statements in the loop can read the value of the index, but cannot change it. If not, the program flow moves to the following block of code after the loop. The GOTO statement can then make use of this user-defined name to jump into that block of code for execution. The inner loop has two EXIT WHEN statements; one that exits the inner loop and one that exits the outer loop. It is used when a set of statements should be executed as long as condition is true. It contains a block of code with keywords ENDIF and THEN. Code line 8: Since condition2 failed, then the condition3 40>mark>=35 is checked. In Example 4-11, one basic LOOP statement is nested inside the other, and both have labels. BEGIN In conditions where we are using nested loops, the EXIT statement will first terminate the inner loop and then execute the block of code that appears immediately after it. i := i+1; The IF and CASE statements let you branch program execution according to one or more conditions. The GOTO statement transfers control to a label unconditionally. a := a + 1;

intellipaat