SQL for Everyday Use
Read, filter, join
Qardbox is a free flashcard app for iPhone, iPad and Apple Watch, with no ads and with your data staying yours. It costs nothing, asks for no account and shows no ads, and your own cards stay unlimited. That is a promise.
You can always create as many flashcards as you like, free of charge.
If you would rather use a ready-made deck such as SQL for Everyday Use, we ask you for a small sum in return. For €1.29 once you get 28 flashcards, sorted into 5 categories and with notes that add to them. You start out learning instead of typing, and whatever you find missing later you add yourself.
- Cards
- 28
- Categories
- 5
- Price
- €1.29
Free, no account, no ads
What is in this deck
With this deck you learn the SQL queries that carry daily work: select, filter, sort, group and join.
UPDATE table SET a = 1 without WHERE changes every row. You read that once in a note and never again in an incident report.
This deck asks about the task, not the syntax: "How do you filter after grouping?" The answer is the query. 15 of the 28 cards carry a note, and each one warns or distinguishes, WHERE against HAVING, **COUNT(*) against COUNT(column)**, and why = NULL is never true.
Standard SQL, no dialect. Where systems differ, the note says so.
The categories decide what comes up: start with “Filtering and sorting” alone and add the rest when you are ready.
What you learn
- 28 queries from SELECT to transactions
- WHERE vs HAVING, COUNT(*) vs COUNT(a)
- Why UPDATE without WHERE is dangerous
The categories
5 categories sort the 28 cards. You can filter by category and take on what is due right now.
- Filtering and sorting
- Grouping
- Joining
- Reading
- Writing and structure
What you get
Here are three of the 28 cards you get when you buy the deck.
Question
How do you fetch all rows and columns of a table?
Answer
**SELECT * FROM tabelle**
Note
The star has a price. In applications you name the columns you need, otherwise the query breaks as soon as someone adds one.
Question
How do you fetch only two columns?
Answer
SELECT a, b FROM tabelle
Note
Question
How do you give a column a different name in the result?
Answer
SELECT a AS name FROM tabelle
Note
Learning with Qardbox
You see a card, you think, you turn it over and say whether you knew it. A round asks nothing more of you, and how the app works out the next date from that is on the page about FSRS-6.
What sits comes back less often, what wobbles comes back soon. You set a daily goal, and when nothing is due the app tells you exactly that instead of inventing work for you. How a round goes is shown on the learning page.
Everything stays on your device. No account, no sign-up, no ads. After the purchase the deck sits in your library like any other subject and can be studied, reordered and extended just like your own.
What it costs, and what it doesn’t
Qardbox itself costs nothing, and it stays that way. Every function is there from the start, with no subscription, no ads and no tiers; what that rests on is on the page about what it costs.
Your own cards stay unlimited, and decks from friends or from the family you read in without a limit, from a file as well. You do not need this deck in order to learn with Qardbox.
It is a shortcut: 28 checked cards for €1.29, once, with Family Sharing. The work you would otherwise do is already done. The App Store shows the price in your currency.
Common questions
Do I have to pay for Qardbox?
No. The app is free, with no subscription and no ads, and every feature is included. The only thing that costs money is a ready-made deck like this one, €1.29 once.
Could I make these cards myself?
Yes, without limit and for free. You can type them, import a file or take over cards from friends. This deck only saves you the work.
How many cards are in SQL for Everyday Use?
28 cards, sorted into 5 categories.
Do I need a connection to study?
Only to download the deck. After that it lives on your device and you study offline. There is no account, and you sign in nowhere.
Which devices does this run on?
On iPhone and iPad from iOS 26, and on Apple Watch. One purchase covers the family through Family Sharing.
Is there a Qardbox for Android?
No. Qardbox is there for iPhone, iPad and Apple Watch, not for Android and not in a browser.
Other decks that go with this one
Get started
Get Qardbox, look at the deck in the store and decide there. The app is free whether you take this deck or not.
Free on the App Store, no account.