SQL Filters: WHERE vs. HAVING in Data Filtering

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In SQL, both the WHERE and HAVING clauses are used to filter data, but they are used in different contexts and with different purposes.

I. WHERE Clause:

• The WHERE clause is used with the SELECT, UPDATE, DELETE, and INSERT statements to filter rows based on a specified condition.
• It is primarily used for filtering rows before they are grouped and aggregated.
• It operates on individual rows before any grouping or aggregation takes place.
• Commonly used for conditions involving columns present in the individual rows.

SELECT column1, column2
FROM table_name
WHERE condition;

II. HAVING Clause:

• The HAVING clause is used with the SELECT statement and is specifically used with aggregate functions like COUNT, SUM, AVG, etc.
• It is used to filter the results of a grouped query, specifying conditions on the result of aggregate functions.
• It operates on grouped rows, after the GROUP BY clause, and filters the result set based on aggregated values.
• Commonly used for conditions involving the result of aggregate functions.

SELECT column1, column2, aggregate_function(column3)
FROM…