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N053-H2 Tier 4 · Advanced · hard ecommerce · Brightlane

Return the ID and name of every product whose `'gps'` attribute is the boolean true value

Part of JSONB Field Extraction in SQL

The problem

Brightlane's device inventory system identifies products that include GPS functionality. The GPS feature is recorded as a JSONB boolean within each product's attributes.

Write a query to return the ID and name of every product whose 'gps' attribute is the boolean true value.

Assumptions:

  • Some products have a 'gps' key in attributes whose value is a JSONB boolean (true or false). Other products have no 'gps' key on record.
  • A GPS-enabled product has its 'gps' key set to JSONB true. The text representation of JSONB true is the string 'true'.
  • Only GPS-enabled products should appear.

Output:

  • One row per qualifying product, with columns id and name.
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
  id,
  name
FROM
  products
WHERE
  attributes ->> 'gps' = 'true'

The shape

JSONB booleans extract to the text strings 'true' and 'false' via ->>. So a filter for GPS-enabled products compares the text result against the literal 'true'. The comparison stays in text on both sides, which is the simpler shape than casting to boolean and comparing against the boolean literal.

Clause by clause

  • SELECT id, name returns the product's ID and name. No JSONB extraction is needed in the output because the inventory system only wants the list of GPS-enabled products, not the GPS value itself.
  • FROM products reads the product catalog.
  • WHERE attributes ->> 'gps' = 'true' extracts the value at the 'gps' key as text and keeps the row only when that text is exactly 'true'. Products with no 'gps' key extract to NULL (filtered out by the equality), products with 'gps' set to JSONB false extract to 'false' (also filtered out), and only products with 'gps' set to JSONB true survive.

Why this and not (attributes ->> 'gps')::boolean = true

The cast version works, and on a single value the runtime cost is negligible. But it's more characters of SQL for no semantic gain — both forms produce the same result. The text comparison is also more forgiving: if the JSONB document happens to carry a text 'true' instead of a boolean true (a real possibility when JSONB is produced by several different upstream systems), the text comparison catches both representations while the boolean cast would raise an error on the text form.

The trap

The string 'true' is case-sensitive. PostgreSQL renders JSONB booleans as lowercase 'true' and 'false', so comparing against 'True' or 'TRUE' would never match anything coming out of ->>. The boolean cast (::boolean) is more permissive — it accepts 'TRUE', 't', 'yes', and a few others — but that permissiveness only kicks in when the cast is the comparison mechanism. With the text form chosen here, the literal on the right has to match exactly what ->> produces, which is always the lowercase form.

You practiced ->> against a JSONB boolean — ->> returns the text form ('true' or 'false'); equality against the string literal works correctly without an explicit cast to boolean.

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