SQL Lab — JOINs Under Pressure

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SQL Terminal

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Schema Map

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Questions

📌 BUSINESS QUESTIONS

○INNER JOIN: orders + customers

○LEFT JOIN: find unassigned orders

○3-table JOIN: reps + regions + orders

○Answer: North region reps > £10k

○RIGHT JOIN: all products + sales

○Final answer submitted

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SQL TERMINAL — company_db (5 tables)

MySQL 8.0 — company_db loaded Tables: orders, customers, reps, regions, products ⚠ No documentation found. Map the relationships yourself. Hint: use DESCRIBE <table> to inspect foreign keys ──────────────────────────────────────────────

mysql>

RELATIONSHIP MAP — company_db

regions

⚿ id

name

←1:N→

reps

⚿ id

full_name

⚷ region_id

hire_date

←1:N→

orders

⚿ id

⚷ rep_id

⚷ customer_id

⚷ product_id

amount_gbp

order_date

←N:1→

customers

⚿ id

company_name

country

←N:1→

products

⚿ id

name

MISSION BRIEFING

JOIN ANALYSIS — VANTAGE DISTRIBUTION

SCENARIO

Vantage Distribution's previous analyst left no documentation. You have five tables and a set of business questions from the Sales Director that need answering today. Figure out the relationships and write the JOIN queries to get the answers.

JOIN SYNTAX

INNER JOIN — only matching rows in both tables
LEFT JOIN — all left rows, NULLs for no match on right
RIGHT JOIN — all right rows, NULLs for no match on left
Syntax: FROM tableA a JOIN tableB b ON a.id = b.a_id

KEY QUERY TEMPLATE

SELECT r.full_name, rg.name AS region, SUM(o.amount_gbp) FROM orders o JOIN reps r ON o.rep_id=r.id JOIN regions rg ON r.region_id=rg.id WHERE rg.name='North' GROUP BY r.full_name HAVING SUM(o.amount_gbp) > 10000;

TIP

Open the Schema Map window to see how the foreign keys connect the tables. Start with a simple 2-table JOIN, then add more tables one at a time.

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