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N032-E1 Tier 3 · Intermediate · easy ecommerce · Brightlane

Return the string `'1992-04-18'` cast as a calendar date

Part of Date and Time Types in PostgreSQL in SQL

The problem

Brightlane's data engineering team is verifying that plain date strings parse cleanly to the calendar-date type during import.

Write a query to return the string '1992-04-18' cast as a calendar date.

Output:

  • A single row with one column, birth_date, typed as a date.
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
  '1992-04-18'::date AS birth_date

The shape

The ::date cast tells PostgreSQL to resolve '1992-04-18' as a calendar date rather than as the text it would otherwise be. A birth date has no time-of-day and no time zone, which is exactly what DATE stores.

Clause by clause

  • SELECT '1992-04-18'::date AS birth_date evaluates the literal once and returns it as a single DATE value. The ::date cast is the load-bearing part: without it, PostgreSQL would resolve the literal as text, and the output column would carry the wrong type even though the displayed string looks identical.
  • There is no FROM because no table is being read; the value comes directly from the literal in the SELECT list.

Why the explicit cast

A bare '1992-04-18' is just a string. PostgreSQL will display it the same way in a result row, but downstream consumers that expect a date column will see text and either error out or coerce silently. The ::date cast resolves the ambiguity at write time and locks the column's type to DATE. The alternate spelling CAST('1992-04-18' AS date) produces the same result; pick whichever reads more naturally in context.

You practiced casting a calendar-only string to DATE with ::date — the right type for values that have no time-of-day component.

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