使用LEFT JOIN進行MySQL查詢，並具有來自另一個表的OrderID的計數…卡住了

Question

這是我當前的查詢，並且按預期工作正常。

SELECT a.ID, a.CreatedDate, a.Status, b.OrderTotal, 
    e.Rate, f.RouteType, f.Code, g.Country, h.Network 
    from orders AS a
     LEFT JOIN order_details AS b ON a.ID = b.OrderID
     LEFT JOIN order_routes AS d ON a.ID = d.OrderID
     LEFT JOIN userrate AS e ON e.ID = d.RouteID
     LEFT JOIN ratelist AS f ON f.ID = e.RateListID
     LEFT JOIN country AS g ON f.CountryID = g.ID
     LEFT JOIN network AS h ON f.NetworkID = h.ID
     WHERE a.UserID = 16 ORDER BY a.CreatedDate DESC

但是，現在我試圖添加另一列，該列向我顯示order_routes中每個OrderID的出現次數

我的訂單路線現在看起來像這樣

ID   OrderID   RouterID
1      1         1
2      1         2
3      2         2
4      2         3
5      2         5

所以我想要一列，該列向我顯示Order_routes表中有多少OrderID外觀。

我想我的查詢中需要子查詢，但是當我嘗試它給我錯誤時。 讓你知道

a.ID = d.OrderID

e.ID = d.RouteID

請幫忙。

Answer 1

嘗試這個

SELECT a.ID, a.CreatedDate, a.Status, b.OrderTotal, 
    e.Rate, f.RouteType, f.Code, g.Country, h.Network, d2.cnt AS OrderCount 
FROM orders AS a
    LEFT JOIN order_details AS b ON a.ID = b.OrderID
    LEFT JOIN order_routes AS d ON a.ID = d.OrderID
    LEFT JOIN (SELECT OrderID as OrderID2, COUNT(*) AS cnt FROM order_routes GROUP BY 1) AS d2 ON a.ID = d2.OrderID2
    LEFT JOIN userrate AS e ON e.ID = d.RouteID
    LEFT JOIN ratelist AS f ON f.ID = e.RateListID
    LEFT JOIN country AS g ON f.CountryID = g.ID
    LEFT JOIN network AS h ON f.NetworkID = h.ID
    WHERE a.UserID = 16 ORDER BY a.CreatedDate DESC