MySQL запрос нескольких подзапросов group_concat

Question

Я пытаюсь показать районы и почтовые индексы, в которых находится конкретный город.

Моя база данных довольно хорошо структурирована, с таблицей, такой как город, почтовый индекс и район. Есть также таблицы для каждого из отношений town_postcode & town_borough.

В идеале я хочу, чтобы данные возвращались как:

"Abbey Wood", "SE2", "Bexley, Greenwich" "Барбакан", "EC1, EC2", "Лондонский Сити"

Я пробовал несколько разных подходов, и я близок, но пока нет.

Любая помощь будет оценена ... :) Пока я пробовал

SELECT DISTINCT t.town, 
GROUP_CONCAT( DISTINCT p.postcode SEPARATOR ', ' ) AS 'postcode', 
GROUP_CONCAT( DISTINCT b.borough SEPARATOR ', ' ) AS 'borough'
FROM coverage_towns AS t, 
coverage_boroughs AS b, 
coverage_postcodes AS p, 
coverage_towns_boroughs AS tb, 
coverage_towns_postcodes AS tp
WHERE t.id = tp.town_id
AND p.id = tp.postcode_id
AND b.id = tb.borough_id
GROUP BY t.town
ORDER BY t.town ASC

Что возвращает

"Abbey Wood", "SE2", "Southwark, Hammersmith and Fulham, Tower Hamlets, Wandsworth, Enfield, Newham, LOTS MORE HERE"
"Barbican", "EC1, EC2", "Brent, Greenwich, Kensington and Chelsea, Westminster, Camden, LOTS MORE HERE"

Я тоже пробовал

SELECT DISTINCT t.town, (

SELECT SQL_CACHE DISTINCT GROUP_CONCAT( p1.postcode
SEPARATOR ', ' )
FROM coverage_postcodes AS p1
WHERE p1.id = tp.postcode_id
) AS 'postcode', (

SELECT SQL_CACHE DISTINCT GROUP_CONCAT( b1.borough
SEPARATOR ', ' )
FROM coverage_boroughs AS b1
WHERE b1.id = tb.borough_id
) AS 'borough'
FROM coverage_towns AS t, coverage_boroughs AS b, coverage_postcodes AS p, coverage_towns_boroughs AS tb, coverage_towns_postcodes AS tp
WHERE t.id = tp.town_id
AND p.id = tp.postcode_id
AND b.id = tb.borough_id
GROUP BY t.town
ORDER BY t.town ASC

Что возвращает

"Abbey Wood", "SE2", "Greenwich"
"Acton", "W3", "Greenwich"
"Aldersbrook", "E12", "Greenwich"

Answer 1

РЕШЕНИЕ

Я вернулся к вопросу после хорошего кофе, и ответ дал себя.

SELECT DISTINCT t.town, 
GROUP_CONCAT( DISTINCT p.postcode SEPARATOR ', ' ) AS 'postcode', 
GROUP_CONCAT( DISTINCT b.borough SEPARATOR ', ' ) AS 'borough'
FROM towns AS t, boroughs AS b, postcodes AS p, towns_boroughs AS tb, towns_postcodes AS tp
WHERE (t.id = tp.town_id AND t.id = tb.town_id)
AND (p.id = tp.postcode_id AND b.id = tb.borough_id)
GROUP BY t.town
ORDER BY t.town ASC

Answer 2

Первый запрос выглядит хорошо, просто добавьте distinct внутри group_concat, например:

SELECT  t.town
,      GROUP_CONCAT(DISTINCT p.postcode SEPARATOR ', ' ) AS 'postcode'
,      GROUP_CONCAT(DISTINCT b.borough SEPARATOR ', ' ) AS 'borough'
<more code here>
GROUP BY
        t.town