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N034-M1 Tier 3 · Intermediate · medium ecommerce · Brightlane

Return the new start time produced by adding `3` hours to the timestamp `'2024-01-15 09:00:00'`

Part of Date Arithmetic and Intervals in SQL

The problem

Brightlane's event scheduling platform shifts a meeting start time forward by 3 hours to accommodate a rescheduled call.

Write a query to return the new start time produced by adding 3 hours to the timestamp '2024-01-15 09:00:00'.

Output:

  • A single row with one column, new_start_time, typed as a timezone-naive timestamp.
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
  '2024-01-15 09:00:00'::TIMESTAMP + INTERVAL '3 hours' AS new_start_time

The shape

Adding INTERVAL '3 hours' to a timestamp shifts that timestamp forward by three hours and returns a value of the same timestamp type. The meeting that was at nine in the morning becomes a meeting at noon, with the rest of the calendar position untouched.

Clause by clause

  • SELECT '2024-01-15 09:00:00'::timestamp + INTERVAL '3 hours' AS new_start_time builds the rescheduled start time. The ::timestamp cast pins the literal as a timezone-naive timestamp, which is the type the scheduling platform stores. Adding an INTERVAL of three hours advances the time-of-day component without crossing a calendar boundary in this case. The alias AS new_start_time labels the output.

Why the result is a TIMESTAMP and not a DATE

When an INTERVAL is added to a DATE, TIMESTAMP, or TIMESTAMPTZ, the return type is the same as the input. Because the left side is TIMESTAMP, the result is TIMESTAMP. The hours-and-minutes precision of the source value is preserved through the arithmetic, which is what a scheduling system needs: shifting a meeting by three hours has to land on a value that still carries a time-of-day, not a value that collapses to midnight.

You practiced timestamp + INTERVAL '3 hours' — shift a point in time forward by a sub-day duration.

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