Difference between WHERE clause and HAVING clause in MySQL




Hello and welcome everyone. In this article, we will learn about the difference between Where clause and Having clause. Let’s go.
WHERE clause and HAVING clause

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              WHERE clause is used to get a specific result with a specific condition and also it filters records.
HAVING clause is used with the GROUP BY clause to filter group values.

              WHERE clause is not used aggregated data, it used with row’s data.
HAVING clause used aggregated data for filter values from the group.

              WHERE clause is used with SELECT statement, UPDATE statement and DELETE statement.
HAVING clause is used with an only SELECT statement.

              WHERE clause has built-in operation and indexes are set, so filter result comes fast.
HAVING clause firstly filter query and after that, it saved, gathered and after that sorted results, so it’s slow than WHERE clause.
             
              WHERE clause is used for row operations.
Having clause is used for column operations.

              WHERE clause aggregate functions not use because this function only performed on columns,
Having clause is used for column operations; therefore we can use aggregate functions.

              WHERE clause checked condition while query running. 
HAVING clause already found query result.

              WHERE clause is used before the GROUP BY clause.
HAVING clause is used after GROUP BY clause.

              WHERE clause used without GROUP BY clause.
Having clause not use without GROUP BY clause.

              WHERE clause before grouping it selects rows.
HAVING clause after grouping selects rows.

Syntax of WHERE clause
                SELECT *
FROM table_name
WHERE condition;
Syntax of HAVING clause
              SELECT column_name_1, column_name_2, aggregate_function
              FROM table_name
              WHERE condition
              GROUP BY column_name
              HAVING condition
              ORDER BY column_name;




              Example of WHERE clause
               SELECT
           e_id, e_name
                     WHERE Age > 20;
Example of HAVING clause
               SELECT e_firstname as Fname, e_lastname as Lname
               FROM employee
               GROUP BY e_sex
               HAVING e_age > 25;

In this article, we learned the difference between WHERE clause and HAVING clause with their syntax and example.

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