通過聯接從多個表中選擇列

Question

我有兩個桌子：

users (username, business_id, etc.)

businesses (business_id, service_type, latitude, longitude, etc.)

我有以下查詢，可以正常工作：

SELECT username, users.business_id FROM users JOIN businesses 
ON users.business_id = businesses.business_id WHERE service_type = ?

現在，我想在結果中也有“ 企業 ”表中的“ 緯度 ”和“ 經度 ”列。 我怎樣才能做到這一點？

我嘗試執行以下操作，但出現錯誤：

SELECT username, users.business_id, businesses.latitude, businesses.longitude 
FROM users, businesses JOIN businesses 
ON users.business_id = businesses.business_id WHERE service_type = ?

什么是獲得所需結果的正確方法？

Answer 1

您在where部分兩次有業務：

FROM users, businesses JOIN businesses

刪除第一個，應該像之前一樣：

FROM users JOIN businesses

Answer 2

使用顯式聯接語法：

SELECT username, users.business_id, 
       businesses.latitude, businesses.longitude 
FROM users 
JOIN businesses 
   ON users.business_id = businesses.business_id 
WHERE service_type = ?

您正在將隱式與顯式語法混合在一起。 因此, businesses實際上沒有必要在FROM子句中使用, businesses 。

Answer 3

有一個使用JOIN語法的錯字，請嘗試以下操作：

SELECT users.username, users.business_id, businesses.latitude, businesses.longitude 
FROM users JOIN businesses ON users.business_id = businesses.business_id 
WHERE service_type = ?