SQL COUNT Function - Complete Beginner Tutorial

Count Total Orders

Write a SQL query to count the total number of orders in an Orders table.

Expected output: A single number representing total orders.

Hint: Use COUNT(*) to count all rows.

Count Non-Null Customer IDs

Write a SQL query to count how many orders have a non-null CustomerID.

Expected output: A single number representing orders with customers.

Hint: Use COUNT(CustomerID) to exclude nulls.

Count Orders per Status

Write a SQL query to count the number of orders for each order status.

Expected output: A list of order statuses with their counts.

Hint: Use GROUP BY OrderStatus with COUNT(*).

COUNT(*) counts all rows including those with nulls, while COUNT(column_name) counts only rows where the specified column is not null.

Use COUNT(DISTINCT column_name) to count the number of unique non-null values in that column.

Yes, COUNT can be combined with GROUP BY to count rows within each group, allowing segmented aggregation.