How to get different distinct sales from same table - mysql

Question

Im having trouble to get the distinct sales from my DB, I tried INNER JOIN but it doesn't work. My SQL statement is something like this:
SELECT * FROM (SELECT DISTINCT(mta.Maintenance.userId) AS a
FROM mta.Maintenance WHERE 1=1) AS t
INNER JOIN mta.Maintenance
ON t.a = mta.Maintenance.userId
WHERE 1=1
AND mta.Maintenance.paymentStatus = 'PAID'
AND mta.Maintenance.createdAt < 1648771199000
AND mta.Maintenance.createdAt > 1640995199000
AND mta.Maintenance.deletedAt IS NULL
AND mta.Maintenance.price > 50
And the table is something like this:
a
maintenanceId
adminId
storeId
vehicleId
serviceId
paymentStatus
status
createdAt
userId
65
50
\N
6
26
38
PAID
PENDING
1644237405347
65
71
70
28
3
32
32
PAID
PENDING
1644499807732
71
71
72
52
3
34
30
PAID
PENDING
1644851796531
71
78
75
52
6
36
38
PAID
PENDING
1644858138158
78
78
76
52
6
37
91
PAID
PENDING
1644863060421
78
And I want:
a
maintenanceId
adminId
storeId
vehicleId
serviceId
paymentStatus
status
createdAt
userId
65
50
\N
6
26
38
PAID
PENDING
1644237405347
65
71
70
28
3
32
32
PAID
PENDING
1644499807732
71
78
75
52
6
36
38
PAID
PENDING
1644858138158
78
Basically the distincts results with the MIN(createdAt).
Thanks!!

Answer 1

Try using ROW_NUMBER() to group the rows by UserId and assign a sort number based on the CreatedAt value. Then grab rows where SortNum = 1
WITH cte AS (
SELECT *, ROW_NUMBER() OVER(PARTITION BY UserId ORDER BY CreatedAt ASC) AS SortNum
FROM Maintenance
)
SELECT *
FROM cte
WHERE RowNum = 1
a
maintenanceId
adminId
storeId
vehicleId
serviceId
paymentStatus
status
createdAt
userId
RowNum
65
50
N
6
26
38
PAID
PENDING
1644237405347
65
1
71
70
28
3
32
32
PAID
PENDING
1644499807732
71
1
78
75
52
6
36
38
PAID
PENDING
1644858138158
78
1
db<>fiddle here

Answer 2

Try using the MySQL IN Operator of MySQL and from there select the min(createdat) column and group them by a in the main query.
SELECT * FROM maintenance a
WHERE createdat
IN (SELECT MIN(createdat) FROM maintenance b WHERE b.a=a.a)
GROUP BY a;
RESULT
a maintenanceId adminId storeId vehicleId serviceId paymentStatus STATUS createdAt userId
------ ------------- ------- ------- --------- --------- ------------- ------- ------------- --------
65 50 (NULL) 6 26 38 PAID PENDING 1644237405347 65
71 70 28 3 32 32 PAID PENDING 1644499807732 71
78 75 52 6 36 38 PAID PENDING 1644858138158 78