A finance director is reviewing the department budget summary before submitting it for approval. The summary must show three figures:
- Development cost of
$12,000 - Operations cost of
$4,500 - The total of the two
Write a query to return all three in a single row.
Output:
- A single row with three columns:
development_cost,operations_cost, andtotal_cost.
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SELECT
12000 AS development_cost,
4500 AS operations_cost,
12000 + 4500 AS total_costThe shape
Two labeled cost figures and a total expression that adds them up, all returned as three columns in a single row — the line items the finance director needs to defend the budget, plus the roll-up that goes on the cover page.
Clause by clause
12000 AS development_costis a labeled integer literal — the development line item, named so it reads as a budget row rather than as a number.4500 AS operations_costis the second labeled literal, the operations line item. Same shape as the first column.12000 + 4500 AS total_costis the roll-up: the two line items added together, returning16500. Both operands are integers, so the result is the integer16500— clean for a budget summary that doesn't deal in cents.
Why this and not development_cost + operations_cost AS total_cost
The natural shape would be to reference the aliases — development_cost + operations_cost — since the prompt describes the total in those terms. SQL won't allow it inside the same SELECT list. Every expression in SELECT evaluates against the same input at the same time, and the aliases only come into being as labels on the way out. By the time development_cost is a usable name, the row is already finished. So the total has to be written from the underlying literals: 12000 + 4500.
The repetition is the price of producing the breakdown and the total side by side in one query. The same two numbers appear twice — once as their own columns, once as the operands of the sum. At this scale, it's the shape; later, with subqueries and CTEs available, a value computed once and reused becomes possible. For now, the inline repetition is what makes a one-row summary work.
You practiced producing a derived column alongside the inputs that built it. Holding both the components and the aggregate on one row is the recurring shape behind any line-item summary — the reader sees the parts and the whole side by side.
