open folder

Query Cheat Sheet

The only SQL you need

1 · Filter and sort

SELECT column1, column2
FROM some_table
WHERE column1 = 'value'
ORDER BY column2 DESC;

2 · Add up per group

SELECT column1, COUNT(*), SUM(amount)
FROM some_table
GROUP BY column1;

3 · Combine two tables

SELECT a.*, b.name
FROM table_a AS a
JOIN table_b AS b ON a.shared_id = b.shared_id;

Tips: text goes in 'single quotes'. Dates look like '2026-03-19'. WHERE description LIKE '%fog%' finds text containing "fog".

Accounting in five minutes

The accounting equation

Assets = Liabilities + Equity

Assets: what the company owns (cash, equipment, prepaid insurance).
Liabilities: what it owes (Accounts Payable: bills not yet paid).
Equity: what belongs to the owners.

During the year, revenue adds to equity and expenses take it away, so:

Assets = Liabilities + Equity + Revenue − Expenses

Debits and credits keep it balanced

Every journal entry has debits and credits, and they always add up to the same amount. Assets and expenses grow with debits; liabilities, equity and revenue grow with credits.

A normal purchase takes two entries

When	Account	Debit	Credit
The bill arrives	Smoothie Bar Supplies (expense)	300.00
The bill arrives	Accounts Payable		300.00
We pay the bill	Accounts Payable	300.00
We pay the bill	Cash at Bank		300.00

Expense or asset?

An expense is used up: smoothie cups, props for one episode, villa rent.
An asset is something the company keeps and uses over time: cameras, buildings, land.
Prepaid items are assets for a short while: you pay a year of insurance up front, then expense it month by month.

Act 0 · Practice case: who keeps over-ordering the smoothie cups?

We solve this one together on the projector. Table smoothie_cup_orders:

order_id	order_date	ordered_by	cups	cost_rm
1	2026-08-03	orangelo	200	60.00
2	2026-08-04	grapenzo	1500	450.00
3	2026-08-05	pineapena	150	45.00
4	2026-08-06	cherrita	100	30.00
5	2026-08-07	grapenzo	1800	540.00
6	2026-08-10	orangelo	250	75.00
7	2026-08-11	kiwilo	120	36.00
8	2026-08-12	grapenzo	2000	600.00
9	2026-08-13	strawberrina	180	54.00
10	2026-08-14	pineapena	200	60.00
11	2026-08-17	grapenzo	1600	480.00
12	2026-08-18	cherrita	90	27.00
13	2026-08-19	orangelo	220	66.00
14	2026-08-20	bananito	300	90.00
15	2026-08-21	grapenzo	1900	570.00
16	2026-08-24	kiwilo	110	33.00
17	2026-08-25	strawberrina	160	48.00
18	2026-08-26	pineapena	210	63.00
19	2026-08-27	grapenzo	2100	630.00
20	2026-08-28	orangelo	240	72.00

Step 1 · Look at everything, sorted

SELECT *
FROM smoothie_cup_orders
ORDER BY cups DESC;

ORDER BY sorts the rows. DESC puts the biggest first.

Step 2 · Narrow it down

SELECT order_date, ordered_by, cups
FROM smoothie_cup_orders
WHERE cups > 1000;

WHERE keeps only the rows that match a condition.

Step 3 · Add it up per person

SELECT ordered_by, COUNT(*) AS orders, SUM(cost_rm) AS total_rm
FROM smoothie_cup_orders
GROUP BY ordered_by
ORDER BY total_rm DESC;

GROUP BY makes one row per person. SUM adds up each person's orders.

Then the accounting question: smoothie cups are booked to 5200 Smoothie Bar Supplies. Is that an expense or an asset, and why?