MySQL 5.6

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE invoice1 (InvoiceID INT, UserID INT);
INSERT INTO invoice1 VALUES
(1230,1),
(1231,3),
(1232,2),
(1233,5),
(1234,8),
(1235,4),
(1236,7),
(1237,6),
(1238,9),
(1239,10);
SELECT * FROM invoice1;


InvoiceID
UserID


1230
1

1231
3

1232
2

1233
5

1234
8

1235
4

1236
7

1237
6

1238
9

1239
10


CREATE TABLE invoice2 (InvoiceID INT, UserID INT);
INSERT INTO invoice2 VALUES
(1230,10),
(1231,9),
(1232,8),
(1233,7),
(1234,6),
(1235,5),
(1236,1),
(1237,2),
(1238,3),
(1239,4);
SELECT * FROM invoice2;


InvoiceID
UserID


1230
10

1231
9

1232
8

1233
7

1234
6

1235
5

1236
1

1237
2

1238
3

1239
4


SELECT InvoiceID, UserID, @num := @num + 1 rownumber
FROM invoice1, (SELECT @num:=0) variable
WHERE InvoiceID > 1234
ORDER BY UserId;


InvoiceID
UserID
rownumber


1235
4
1

1237
6
2

1236
7
3

1238
9
4

1239
10
5


SELECT InvoiceID, UserID, @num := @num + 1 rownumber
FROM invoice2, (SELECT @num:=0) variable
WHERE InvoiceID > 1234
ORDER BY UserId;


InvoiceID
UserID
rownumber


1236
1
1

1237
2
2

1238
3
3

1239
4
4

1235
5
5


SELECT t1.InvoiceID, t1.UserID, t2.InvoiceID, t2.UserID
FROM ( SELECT InvoiceID, UserID, @num1 := @num1 + 1 rownumber
       FROM invoice1, (SELECT @num1 := 0) variable
       WHERE InvoiceID > 1234
       ORDER BY UserId ) t1
JOIN ( SELECT InvoiceID, UserID, @num2 := @num2 + 1 rownumber
       FROM invoice2, (SELECT @num2 := 0) variable
       WHERE InvoiceID > 1234
       ORDER BY UserId ) t2 USING (rownumber)


InvoiceID
UserID
InvoiceID
UserID


1235
4
1236
1

1237
6
1237
2

1236
7
1238
3

1238
9
1239
4

1239
10
1235
5