Join three tables for real insights
A bridge table connects orders to products. Join orders to order_items, then products. Multiply quantity by unit price to calculate line value. Check the grain: one row per item is different from one row per order.
हिन्दी में समझें
order_items ऑर्डर और उत्पाद जोड़ती है। quantity और price से पंक्ति की रकम निकालें। एक item की पंक्ति और एक order की पंक्ति अलग हैं।
अभ्यास: order_id और SUM(quantity * price) AS order_total, order_id अनुसार समूह और क्रम।
Hinglish mein samjhein
order_items orders aur products ko connect karti hai. quantity * price line value hai. Grain samjho: ek item ki row aur ek order ki row alag hain.
Practice: order_id aur SUM(quantity * price) AS order_total, order_id group aur sorted.
A small SQL example
SELECT i.order_id, p.name, i.quantity * p.price AS line_total FROM order_items i JOIN products p ON p.id=i.product_id ORDER BY i.order_id,p.id;Examples use the fictional shop database bundled with the SQL playground: customers, products, orders, order_items and employees. The engine is SQLite; other SQL dialects may differ.
Try this example in the SQL playground →Practise this idea
Return order_id and SUM(quantity * price) as order_total, grouped and ordered by order_id.
Check answer & explanation
SELECT i.order_id, SUM(i.quantity*p.price) AS order_total FROM order_items i JOIN products p ON p.id=i.product_id GROUP BY i.order_id ORDER BY i.order_id;Each item line contributes quantity * price. Grouping by order_id adds those line values into one total per order.
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Check your understanding
To calculate a line total multiply…
Check the quiz answer
quantity by price
A bridge table connects orders to products. Join orders to order_items, then products. Multiply quantity by unit price to calculate line value. Check the grain: one row per item is different from one row per order.
References & corrections
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