Difference Between the HAVING and WHERE Clauses in a SQL

Difference Between the HAVING and WHERE Clauses in a SQL

1. The WHERE clause specifies the criteria which individual records must meet to be selcted by a query. It can be used without the GROUP BY clause. The HAVING clause cannot be used without the GROUP BY clause.
2. The WHERE clause selects rows before grouping. The HAVING clause selects rows after grouping.
3. The WHERE clause cannot contain aggregate functions. The HAVING clause can contain aggregate functions. source
   

   Using the code

   
   
   Code
   
   
   SELECT cusnum, lstnam, init
   
   
   FROM Test
   
   
   WHERE state IN ('CA', 'LA')
   
   
    
   
   
   CUSNUM LSTNAM INIT BALDUE
   
   
   ====== ============ ==== ========
   
   
   938472 John G K 37.00
   
   
   938485 Mark J A 3987.50
   
   
   593029 Lily E D 25.00
   
   
   
   

   Suppose I want the total amount due from customers by state. In that case, I would need to use the GROUP BY clause to build an aggregate query.

   
   
   Code
   
   
   SELECT state,SUM(baldue)
   
   
   FROM Test
   
   
   GROUP BY state
   
   
   ORDER BY state
   
   
    
   
   
   State Sum(Baldue)
   
   
   ===== ===========
   
   
   CA 250.00
   
   
   CO 58.75
   
   
   GA 3987.50
   
   
   MN 510.00
   
   
   NY 589.50
   
   
   TX 62.00
   
   
   VT 439.00
   
   
   WY .00
   
   
   
   

   Using Having

   
   
   Code
   
   
   SELECT state,SUM(baldue)
   
   
   FROM Test
   
   
   GROUP BY state
   
   
   HAVING SUM(baldue) > 250
   
   
    
   
   
    
   
   
   State Sum(Baldue)
   
   
   ===== ===========
   
   
   GA 3987.50
   
   
   MN 510.00
   
   
   NY 589.50
   
   
   VT 439.00