Message Delivery Versus Reads

SQL practice question · Medium · Aggregation · Snapchat

message_events has one row per chat message event (user_id, event_type, event_id) where event_type is 'sent', 'opened' or another value to ignore. For every user who appears in the table, count the messages sent and the messages opened (0 when none). Output columns: user_id, sent_count, opened_count. Order by user_id ascending.

Table: message_events

Schema of message_events
Column	Type
user_id	INTEGER
event_type	TEXT
event_id	INTEGER

Schema of message_events

Column

Type

user_id

INTEGER

event_type

TEXT

event_id

INTEGER

Sample rows of message_events
user_id	event_type	event_id
1	sent	1
1	opened	2
1	sent	3
2	sent	4
2	sent	5
2	opened	6

Sample rows of message_events

user_id

event_type

event_id

sent

opened

sent

opened

Expected output on the sample data
user_id	sent_count	opened_count
1	2	1
2	2	1

Expected output on the sample data

user_id

sent_count

opened_count

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