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-- View all client orders
SELECT *
FROM client_orders;

-- Use WHERE to filter individual rows before grouping
SELECT client_name, region, order_total
FROM client_orders
WHERE region = 'USA';

-- Use HAVING to filter groups after aggregation
SELECT region, AVG(order_total) AS avg_order
FROM client_orders
GROUP BY region
HAVING AVG(order_total) > 200;

# WHERE vs HAVING

In this lesson, you'll learn in detail the difference between `WHERE` and `HAVING`.

Both `WHERE` and `HAVING` are used to **filter data**, but they operate at different stages of a SQL query.

<br/>

## WHERE: Filter Rows Before Aggregation

The `WHERE` clause filters individual records **before** any aggregation or grouping takes place.

```sql title="Filter before grouping"
SELECT client_name, region, order_total
FROM client_orders
WHERE region = 'USA';
```

This returns all orders made by clients from the USA.

<br/>

## HAVING: Filter After Grouping

The `HAVING` clause filters **groups** after aggregation, which is often used with `GROUP BY`.

```sql title="Filter groups after aggregation"
SELECT region, AVG(order_total) AS avg_order
FROM client_orders
GROUP BY region
HAVING AVG(order_total) > 200;
```

This returns only the regions where the average order total is greater than 200.

<br/>

## Summary: When to Use Each

| Clause   | Filters...               | Works With Aggregates?     |
| -------- | ------------------------ | -------------------------- |
| `WHERE`  | Individual rows          | ❌ Not used with aggregates |
| `HAVING` | Groups after aggregation | ✅ Yes                      |

> Use `WHERE` for raw row-level filters.
> Use `HAVING` when filtering aggregated results.

The HAVING clause is specifically used to filter records after they have been grouped and aggregated. While WHERE is used before aggregation to filter rows, HAVING comes into play after the aggregation, allowing you to apply conditions to grouped results. This distinction is vital when working with aggregate functions like SUM, AVG, etc.

### In SQL, which clause would you use to filter groups after an aggregation has been applied?

Clause	Filters...	Works With Aggregates?
`WHERE`	Individual rows	❌ Not used with aggregates
`HAVING`	Groups after aggregation	✅ Yes