Obtaining database joined table with limit [duplicate] - mysql

Question

This question already has answers here:
mysql select top n max values
(4 answers)
Closed 5 years ago.
Ive been trying to join two tables but only showing a limited amount (2) of results from the joined table. Unfortunately I havent been able to obtain the correct results. These are my tables:
Destinations
id name
------------
1 Bahamas
2 Caribbean
3 Barbados
Sailings
id name destination
---------------------------------
1 Adventure 1
2 For Kids 2
3 All Inclusive 3
4 Seniors 1
5 Singles 2
6 Disney 1
7 Adults 2
This is the query Ive tried:
SELECT
d.name as Destination,
s.name as Sailing
FROM destinations d
JOIN sailings s
ON s.destination = d.id
LIMIT 2
But this gives me 2 due to the limit:
Destination Sailing
-------------------------
Bahamas Adventure
Caribbean For Kids
SAMPLE: SQL FIDDLE
I would like LIMIT 2 to be applied only to the joined table sailings
Expected Results:
Destination Sailing
-------------------------
Bahamas Adventure
Bahamas Seniors
Caribbean Singles
Caribbean For Kids
Can someone please point me in the right direction?

Answer 1

try
select tmp.name as destination,d.name as sailings from (
SELECT
id,
name,
destination
FROM
(
SELECT
id,
name,
destination,
#rn := IF(#p = destination, #rn + 1, 1) AS rn,
#p := destination
FROM sailings
JOIN (SELECT #p := NULL, #rn := 0) AS vars
ORDER BY destination
) AS T1
WHERE rn <= 2
)tmp
JOIN (SELECT * FROM destinations limit 0,2) d
ON(tmp.destination=d.id)
I have made 2 derived table and joined them

Answer 2

Your problem is that you want to take the two highest (or lowest) members of a group, for each group in the table. In this case, you want the first two sailings for each destination group.
The canonical way you would handle this query in a database which supported analytic functions would be to use ROW_NUMBER(). But since MySQL does not support this, we can simulate it using session variables:
SET #row_number = 0;
SET #destination = NULL;
SELECT
t.Destination,
t.Sailing
FROM
(
SELECT
#row_number:=CASE WHEN #destination = Destination
THEN #row_number + 1 ELSE 1 END AS rn,
#destination:=Destination AS Destination,
Sailing,
id
FROM
(
SELECT s.id AS id, d.name AS Destination, s.name AS Sailing
FROM destinations d
INNER JOIN sailings s
ON s.destination = d.id
) t
ORDER BY
Destination,
id
) t
WHERE t.rn <= 2
ORDER BY
t.Destination,
t.rn;
Note that Barbados appears as single row, because in your sample data it only has one sailing. If you also want to restrict to only destinations having two or more sailings, this can also be done.
Output:
Demo here:
Rextester

Answer 3

Can you try
SELECT
d.name as Destination,
s.name as Sailing
FROM sailings s
JOIN (SELECT * from destinations LIMIT 2) d
ON s.destination = d.id
(You say you want to limit the sailings table, but I think you might want the limit on the destinations table, based on your expected output; you can adjust as necessary)