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N036-E3 Tier 3 · Intermediate · easy ecommerce · Brightlane

Return the result of combining `'Toronto'`, `'Ontario'`, and `'Canada'` with `CONCAT_WS` using `', '` as the separator

Part of String Concatenation and Formatting in SQL

The problem

Brightlane's address formatter builds location strings by combining a city, region, and country.

Write a query to return the result of combining 'Toronto', 'Ontario', and 'Canada' with CONCAT_WS using ', ' as the separator.

Output:

  • A single row with one column, location, containing the concatenated string with ', ' between every pair of components.
Schema · ecommerce 5 tables
categories
id integer
name text
parent_id? integer
products
id integer
name text
category_id integer
price numeric
stock_qty integer
attributes? jsonb
order_items
id integer
order_id integer
product_id integer
quantity integer
unit_price numeric
customers
id integer
name text
email text
city? text
country text
created_at timestamptz
is_active boolean
orders
id integer
customer_id integer
ordered_at timestamptz
status text
total_amount numeric
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Solution query
SELECT
  CONCAT_WS(', ', 'Toronto', 'Ontario', 'Canada') AS location

The shape

CONCAT_WS(', ', 'Toronto', 'Ontario', 'Canada') takes the separator as its first argument and joins the remaining values with that separator between every pair. The result is 'Toronto, Ontario, Canada' with one ', ' between each component and none at the ends.

Clause by clause

  • SELECT CONCAT_WS(', ', 'Toronto', 'Ontario', 'Canada') AS location evaluates the call and labels the resulting column location. The first argument ', ' is the separator; the remaining arguments are the values to combine. CONCAT_WS walks the value list and inserts the separator between each adjacent pair, but never before the first value or after the last. There is no FROM because all four arguments are literals.

Why this and not 'Toronto' || ', ' || 'Ontario' || ', ' || 'Canada'

Both forms return the same string on this input. CONCAT_WS says the separator once and the values once, which scales cleanly to four, five, or ten components without re-typing the delimiter at each junction. The || chain repeats the separator literal between every pair, which is more to type and more to misread. CONCAT_WS is the right shape whenever the same separator is being inserted between every pair of values.

You practiced CONCAT_WS(separator, ...) — concatenate values with a single separator inserted between every pair, no manual separator-management needed.

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