Select limit result in mysql - mysql

Question

I have table with these data:
Id City Amount
1 London 25000
2 New York 20000
3 London 23000
4 Paris 22000
5 Moscow 18000
6 London 21000
7 New York 19000
8 Moscow 26000
9 London 24000
10 Moscow 16000
11 London 15000
12 Moscow 23000
13 Paris 19000
14 New York 15000
15 London 26000
I must create SQL as what to get the results as this?
Id City Amount
1 London 25000
2 New York 20000
3 London 23000
4 Paris 22000
5 Moscow 18000
7 New York 19000
8 Moscow 26000
13 Paris 19000
That means I just want to get the maximum of one city only to appear 2 times.
I just want to get the first two records or the last two records
Thanks!

Answer 1

If your MySQL version < 8.0, you can simulate RowNumber functionality, using Session variables. To achieve Partition By functionality based on grouping, we will use two session variables, one for the row number and the other for storing the old City to compare it with the current one, and increment it by 1, if belonging to same City group, else reset to 1.
Following code will get your first two records. You can easily change it to get first n records, by changing 2 to n in the query.
SET #row_number = 0;
SET #city_var = '';
SELECT inner_nest.Id,
inner_nest.City,
inner_nest.Amount
FROM (
SELECT
#row_number:=CASE
WHEN #city_var = City THEN #row_number + 1
ELSE 1
END AS num,
Id,
#city_var:=City as City,
Amount
FROM
table_name
ORDER BY
City) AS inner_nest
WHERE inner_nest.num <= 2
ORDER BY inner_nest.Id ASC
**
SQL Fiddle
**