本文介紹了如何在左聯(lián)接中選擇單個記錄的處理方法，對大家解決問題具有一定的參考價值，需要的朋友們下面隨著小編來一起學(xué)習(xí)吧！
問題描述
我需要使用其鍵 ModelID 從 Models 表中選擇一個特定的模型.我還需要從 Model_Content 表中添加一個內(nèi)容簡介.但是，Models_Content 表中的每個模型都有幾個內(nèi)容簡介.我只需要選擇第一個簡介.
I need to select a specific model from the Models table using its key ModelID. I also need to add a blurb of content from the Model_Content table. The Models_Content table, however, has several blurbs of content for each model. I need to select just the first blurb.
我的表格如下所示:
Models // table
ModelID // pk
Model // varchar
Models_Content // table
ContentID // pk
ModelID // fk
Content // varchar
SELECT M.ModelID, M.Model, C.Content
FROM Models M LEFT JOIN Models_Content C ON M.ModelID = C.ModelID
WHERE M.ModelID = 5
如何調(diào)整查詢以僅選擇特定模型的第一個內(nèi)容簡介?
How do I adjust my query to select just the very first blurb of content for a specific model?
推薦答案
SELECT
M.ModelID, M.Model, C.Content
FROM
Models M
LEFT JOIN
Models_Content C
ON C.ContentID = (SELECT MIN(ContentID) FROM Models_Content WHERE ModelID = M.ModelID)
WHERE
M.ModelID = 5
或
;WITH sorted_content AS
(
SELECT
ROW_NUMBER() OVER (PARTITION BY ModelID ORDER BY ContentID) AS itemID,
*
FROM
Models_Content
)
SELECT
M.ModelID, M.Model, C.Content
FROM
Models M
LEFT JOIN
sorted_content C
ON C.ModelID = M.ModelID
AND C.itemID = 1
WHERE
M.ModelID = 5
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