我有三個關係表,結構樣本如下。DISTINCT值來自SQL中的RIGHT JOIN
properties:
property_id | property_name | county_id
------------|---------------|-------
1 | Davis Court | 2
2 | Rose Lodge | 1
3 | Haven Court | 4
4 | Great Lodge | 1
5 | Lilly Court | 2
6 | Miles Lodge | 4
7 | Priory Court | 5
testimonials:
testimonlal_id | property_id | message
---------------|-------------|------------------
1 | 4 | blah blah blah
2 | 2 | blah blah blah
3 | 6 | blah blah blah
4 | 3 | blah blah blah
5 | 1 | blah blah blah
6 | 7 | blah blah blah
7 | 5 | blah blah blah
counties:
county_id | county_name
----------|----------------
1 | Berkshire
2 | Devon
3 | Essex
4 | Kent
5 | Surrey
我想爲表格中的所有感言顯示不同的縣名。我目前有以下查詢。
SELECT DISTINCT properties.county_id, counties.county_id,
counties.county_name, testimonials.testimonial_id
FROM properties
LEFT JOIN counties
ON properties.county_id = counties.county_id
RIGHT JOIN testimonials
ON properties.property_id = testimonials.property_id
ORDER BY properties.county_id ASC
目前這讓我
Berkshire
Berkshire
Devon
Devon
Kent
Kent
Surrey
但我想
Berkshire
Devon
Kent
Surrey
這可能需要的BY運營商使用UNION或GROUP的,但我不知道該如何去適應查詢。
在此先感謝
你是選擇4列,只想要一個?刪除不需要的列 – JohnHC
有多個'testimonial_id',當然你會得到重複的縣名 –
我不明白那些外部連接(好吧,右外連接是難以閱讀,並與q的左外連接混合可怕的。)你想達到什麼目的?有沒有財產證明?沒有縣可以有房產嗎?你也許也在尋找沒有財產的縣?和/或沒有推薦的屬性? –