PL/SQL - Comparison Operators


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Comparison operators are used for comparing one expression to another. The result is always either TRUE, FALSE or NULL.

Operator Description Example
LIKE The LIKE operator compares a character, string, or CLOB value to a pattern and returns TRUE if the value matches the pattern and FALSE if it does not. If 'Zara Ali' like 'Z% A_i' returns a Boolean true, whereas, 'Nuha Ali' like 'Z% A_i' returns a Boolean false.
BETWEEN The BETWEEN operator tests whether a value lies in a specified range. x BETWEEN a AND b means that x >= a and x <= b. If x = 10 then, x between 5 and 20 returns true, x between 5 and 10 returns true, but x between 11 and 20 returns false.
IN The IN operator tests set membership. x IN (set) means that x is equal to any member of set. If x = 'm' then, x in ('a', 'b', 'c') returns Boolean false but x in ('m', 'n', 'o') returns Boolean true.
IS NULL The IS NULL operator returns the BOOLEAN value TRUE if its operand is NULL or FALSE if it is not NULL. Comparisons involving NULL values always yield NULL. If x = 'm', then 'x is null' returns Boolean false.

LIKE Operator

This program tests the LIKE operator. Here, we will use a small procedure() to show the functionality of the LIKE operator −

DECLARE 
PROCEDURE compare (value  varchar2,  pattern varchar2 ) is 
BEGIN 
   IF value LIKE pattern THEN 
      dbms_output.put_line ('True'); 
   ELSE 
      dbms_output.put_line ('False'); 
   END IF; 
END;  
BEGIN 
   compare('Zara Ali', 'Z%A_i'); 
   compare('Nuha Ali', 'Z%A_i'); 
END; 
/

When the above code is executed at the SQL prompt, it produces the following result −

True 
False  

PL/SQL procedure successfully completed.

BETWEEN Operator

The following program shows the usage of the BETWEEN operator −

DECLARE 
   x number(2) := 10; 
BEGIN 
   IF (x between 5 and 20) THEN 
      dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
    
   IF (x BETWEEN 5 AND 10) THEN 
      dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
    
   IF (x BETWEEN 11 AND 20) THEN 
      dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
END; 
/

When the above code is executed at the SQL prompt, it produces the following result −

True 
True 
False 
 
PL/SQL procedure successfully completed.

IN and IS NULL Operators

The following program shows the usage of IN and IS NULL operators −

ECLARE 
   letter varchar2(1) := 'm'; 
BEGIN 
   IF (letter in ('a', 'b', 'c')) THEN 
      dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
  
   IF (letter in ('m', 'n', 'o')) THEN 
       dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
    
   IF (letter is null) THEN 
    dbms_output.put_line('True'); 
   ELSE 
      dbms_output.put_line('False'); 
   END IF; 
END; 
/ 

When the above code is executed at SQL prompt, it produces the following result:

False
True
False

PL/SQL procedure successfully completed.

plsql_operators.htm

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