Счетчик раз ID появляется в таблице и возвращается в строке

Question

SELECT
Boats.id, Boats.date, Boats.section, Boats.raft, 
river_company.company, river_section.section AS river 
FROM Boats 
INNER JOIN river_company ON Boats.raft = river_company.id 
INNER JOIN river_section ON Boats.section = river_section.id 
ORDER BY Boats.date DESC, river, river_company.company

Возвращает все, что мне нужно.Но как добавить таблицу [Photos] и подсчитать, сколько раз в ней встречается Boats.id, и добавить ее к возвращенным строкам.

Так что, если для лодки № 17 есть 5 фотографий, я хочу записатьлодка № 17, чтобы сказать PhotoCount = 5

Answer 1

Вы можете добавить LEFT JOIN к подзапросу следующим образом:

LEFT JOIN (SELECT COUNT(p.id) num, p.boatID FROM photos p GROUP BY p.boatID) 
          sub_photos ON (sub_photos.boatID = Boats.id)

И затем ссылка sub_photos.num в ваших SELECT полях.

Это будет выглядеть примерно так:

SELECT     Boats.id, Boats.date, Boats.section, Boats.raft, 
           river_company.company, river_section.section AS river,
           sub_photos.num AS number_of_photos
FROM       Boats 
INNER JOIN river_company ON Boats.raft = river_company.id 
INNER JOIN river_section ON Boats.section = river_section.id 
LEFT JOIN  (SELECT COUNT(p.id) num, p.boatID FROM photos p GROUP BY p.boatID) 
           sub_photos ON (sub_photos.boatID = Boats.id)
ORDER BY   Boats.date DESC, river, river_company.company

Answer 2

Полагаю, что boatsId - это столбец в таблице фотографий? Самый простой способ был бы с подвыбором:

SELECT ...whatever columns...,

(SELECT COUNT(*) FROM Photos WHERE boatsId = Boats.id)

FROM ...rest of your query

Answer 3

Select YourID, COUNT(*) FROM YourTable GROUP BY YourID

Это прекрасно работает, когда я пытаюсь отследить, где количество записей может отличаться на основе идентификатора или любого другого столбца.

Answer 4

Другой способ

SELECT DISTINCT
Boats.id, Boats.date, Boats.section, Boats.raft,  
river_company.company, river_section.section AS river,
count(photos.boatid) OVER(PARTITION BY photos.boatid)
FROM Boats  
INNER JOIN river_company ON Boats.raft = river_company.id  
INNER JOIN river_section ON Boats.section = river_section.id
LEFT JOIN photos on photos.boatid = Boats.id
ORDER BY Boats.date DESC, river, river_company.company 

Answer 5

Вы не предоставили никакой информации относительно структуры таблицы «Фото», но что-то подобное должно работать для вас.

SELECT
Boats.id, Boats.date, Boats.section, Boats.raft, 
river_company.company, river_section.section AS river,
PhotoCount.NumberOfBoats as PhotoCount 
FROM Boats 
INNER JOIN river_company ON Boats.raft = river_company.id 
INNER JOIN river_section ON Boats.section = river_section.id 
Left Join
(
    Select b2.Id, Count(b2.Id) as NumberOfBoats
    From Boats b2
    Join Photos p on b2.Id = p.BoatId
    Group By b2.Id
)BoatCount on BoatCount.Id = Boats.Id

ORDER BY Boats.date DESC, river, river_company.company

Answer 6

Другой способ:

SELECT 
Boats.id, Boats.date, Boats.section, Boats.raft,  
river_company.company, river_section.section AS river  
Count(Photos.ID) AS PhotoCount
FROM Boats  
INNER JOIN river_company ON Boats.raft = river_company.id  
INNER JOIN river_section ON Boats.section = river_section.id  
OUTER JOIN Photos ON Boats.id = Photos.BoatID ORDER BY Boats.date DESC, river, river_company.company 
GROUP BY
    Boats.id, Boats.date, Boats.section, Boats.raft, river_company.company, river_section.section

Answer 7

SELECT Boats.id,
       Boats.date,
       Boats.section,
       Boats.raft,
       river_company.company,
       river_section.section AS river
       (SELECT count(*) FROM Photos WHERE boatsID = Boats.id)
FROM Boats
INNER JOIN river_company ON Boats.raft = river_company.id 
INNER JOIN river_section ON Boats.section = river_section.id 
ORDER BY Boats.date DESC, river, river_company.company

Дайте этому попробовать.