Volunteer Invitation Acceptance Rate

A community program invites volunteers to join upcoming service projects. An invitation may receive several response updates before the volunteer accepts it.

Table: volunteer_invites

+--------------+-----------+
| Column Name  | Type      |
+--------------+-----------+
| invite_id    | integer   |
| volunteer_id | integer   |
| sent_at      | timestamp |
+--------------+-----------+
+--------------+-----------+
| Column Name  | Type      |
+--------------+-----------+
| invite_id    | integer   |
| volunteer_id | integer   |
| sent_at      | timestamp |
+--------------+-----------+

invite_id is the primary key. Each row represents one invitation sent to a volunteer.

Table: invite_updates

+-----------------+-------------+
| Column Name     | Type        |
+-----------------+-------------+
| update_id       | integer     |
| invite_id       | integer     |
| response_status | varchar(50) |
+-----------------+-------------+
+-----------------+-------------+
| Column Name     | Type        |
+-----------------+-------------+
| update_id       | integer     |
| invite_id       | integer     |
| response_status | varchar(50) |
+-----------------+-------------+

Each row records one response update for an invitation. An invitation can have multiple updates. Some updates may reference an invite_id that is not present in volunteer_invites.

Calculate the invitation acceptance rate: the fraction of invitations in volunteer_invites that have at least one update whose response_status is Accepted.

Count each invitation once, even if it has multiple accepted updates. Invitations with no updates remain in the denominator and are not accepted. Ignore updates that do not match an invitation in volunteer_invites.

Return one row containing acceptance_rate, rounded to two decimal places. Return 0 when there are no invitations.

Output

+-----------------+---------+
| Column Name     | Type    |
+-----------------+---------+
| acceptance_rate | decimal |
+-----------------+---------+
+-----------------+---------+
| Column Name     | Type    |
+-----------------+---------+
| acceptance_rate | decimal |
+-----------------+---------+

Example

Input: volunteer_invites

+-----------+--------------+---------------------+
| invite_id | volunteer_id | sent_at             |
+-----------+--------------+---------------------+
| 125       | 7771         | 2026-06-14 09:00:00 |
| 236       | 6950         | 2026-07-01 10:00:00 |
| 433       | 1052         | 2026-07-09 11:00:00 |
+-----------+--------------+---------------------+
+-----------+--------------+---------------------+
| invite_id | volunteer_id | sent_at             |
+-----------+--------------+---------------------+
| 125       | 7771         | 2026-06-14 09:00:00 |
| 236       | 6950         | 2026-07-01 10:00:00 |
| 433       | 1052         | 2026-07-09 11:00:00 |
+-----------+--------------+---------------------+

Input: invite_updates

+-----------+-----------+-----------------+
| update_id | invite_id | response_status |
+-----------+-----------+-----------------+
| 6878      | 125       | Accepted        |
| 6920      | 236       | Pending         |
| 6994      | 236       | Accepted        |
+-----------+-----------+-----------------+
+-----------+-----------+-----------------+
| update_id | invite_id | response_status |
+-----------+-----------+-----------------+
| 6878      | 125       | Accepted        |
| 6920      | 236       | Pending         |
| 6994      | 236       | Accepted        |
+-----------+-----------+-----------------+

Output:

+-----------------+
| acceptance_rate |
+-----------------+
| 0.67            |
+-----------------+
+-----------------+
| acceptance_rate |
+-----------------+
| 0.67            |
+-----------------+

Explanation: Invitations 125 and 236 are eventually accepted. Invitation 433 has no updates but still counts in the denominator. Two of the three invitations are accepted, so the rate is 0.67.