(because sometimes you need to filter the results after SQL has already grouped the data)
🔧 Quick Syntax
SELECT column, aggregate_function(column)
FROM table
GROUP BY column
HAVING condition;This tells SQL:
“Group the data by a column, apply aggregate functions, and then filter the groups based on a condition.”
👀 Imagine You Have This sales Table Again:
| sale_id | product | quantity | sale_date |
|---|---|---|---|
| 1 | Laptop | 3 | 2024-01-01 |
| 2 | Phone | 5 | 2024-01-01 |
| 3 | Laptop | 2 | 2024-01-02 |
| 4 | Phone | 3 | 2024-01-02 |
| 5 | Laptop | 4 | 2024-01-03 |
| 6 | Phone | 7 | 2024-01-03 |
Scenario: You want to find products where the total quantity sold is greater than 6.
🔧 Using HAVING to Filter Grouped Data
Here’s how to group by product and then use HAVING to filter groups based on the total quantity sold:
SELECT product, SUM(quantity) AS total_quantity
FROM sales
GROUP BY product
HAVING SUM(quantity) > 6;✅ Result:
| product | total_quantity |
|---|---|
| Phone | 15 |
🔁 HAVING vs WHERE
| Clause | When It’s Used |
|---|---|
WHERE | Filters rows before grouping |
HAVING | Filters groups after the data is grouped |
Where to use:
– Use WHERE for filtering individual rows.
– Use HAVING for filtering after the data is grouped.
🧃 Recap
HAVINGis used to filter groups after data has been grouped withGROUP BY.- It is especially useful with aggregate functions (like
SUM,AVG,COUNT) to filter the results based on aggregated values. WHEREfilters data before grouping, whileHAVINGfilters after grouping.