EasySQL challenge #63WHERE

Find Unshipped Orders with IS NULL

Return the orders that are still waiting to ship, the ones with an empty shipped_date.

The challenge runs on the SQLabHub practice database (SQLite) and uses the orders table. You can solve it in the browser, with nothing to install.

Solve This SQL Challenge

The task

Find orders that are not shipped yet.

A correct answer returns 97 rows with 10 columns: id, user_id, total, discount, item_count, status, order_date, shipped_date, shipping_city, shipping_country.

Tables used in this challenge

`orders` 200 rows

id INTEGER (PK) · user_id INTEGER · total REAL · discount REAL · item_count INTEGER · status TEXT · order_date TEXT · shipped_date TEXT · shipping_city TEXT · shipping_country TEXT

First 3 rows of the orders table
id	user_id	total	discount	item_count	status	order_date	shipped_date	shipping_city	shipping_country
1	43	2638.11	0.25	3	cancelled	2024-04-24	NULL	Los Angeles	USA
2	8	2947	0.19	5	delivered	2024-03-15	2023-04-09	Chicago	USA
3	136	683.24	0.08	2	delivered	2023-02-15	2023-07-10	Los Angeles	USA

The first rows of each table are shown. See how all the tables relate on the database schema page.

Expected output

Expected output of the challenge
id	user_id	total	discount	item_count	status	order_date	shipped_date	shipping_city	shipping_country
1	43	2638.11	0.25	3	cancelled	2024-04-24	NULL	Los Angeles	USA
4	115	3920.44	0.08	4	processing	2022-01-10	NULL	San Jose	USA
7	69	1755.54	0.2	2	refunded	2023-03-22	NULL	Philadelphia	USA
9	71	1087.89	0.07	3	cancelled	2023-07-03	NULL	San Antonio	USA
10	23	1356.4	0.23	2	processing	2022-11-05	NULL	Washington DC	USA

First 5 of 97 rows. This is the output of the model solution on the practice database. The task does not fix a sort order, so your rows may come back in a different order.

What you practise

Returning every column of a table with SELECT *
Filtering rows with a WHERE condition
Testing for missing values with IS NULL and IS NOT NULL

Hint and approach

Try the challenge first. Open these only when you need them.

Show the hint

IS NULL

Show the step-by-step approach

How the model solution is built, in the order the database evaluates it:

Read from the orders table.
Filter in WHERE: keep the rows where shipped_date is NULL.
Return every column with SELECT *.

Model solution

Checking your session…

What to watch for

WHERE shipped_date = NULL is valid SQL and always returns nothing. NULL is not equal to anything, including another NULL, so missing values have to be tested with IS NULL.

IS NULL. Comparing with = NULL or <> NULL never matches any row. NULL has to be tested with IS NULL or IS NOT NULL.
WHERE. WHERE is evaluated before the SELECT list, so it cannot use a column alias defined there or the result of an aggregate.
SELECT *. SELECT * is fine for exploring, but its output changes whenever a column is added to the table. Queries that feed a report should name their columns.