mysql聯盟限制問題

Question

我希望分頁腳本能夠正常工作，但情況有點複雜。我需要從兩個SQL查詢的聯合中選擇數據。請參閱下面的查詢。我有一本桌子書和一本桌子書。我想要的是在這裏按照人氣順序顯示特定類別的所有書籍。通過加入餐桌書和書籍，我通過至少一次訪問獲取所有書籍的數據。然後將它與所有沒有訪問的書籍結合起來。一切正常，但當我嘗試做分頁時，我需要將它限制爲（0,10）（10,10）（20,10）（30,10），對嗎？如果我有9本書籍用於該類別，3761本書沒有任何訪問（總共3770本書），它應該列出377頁，每頁上有10本書。但它不顯示任何數據，因爲它試圖顯示限制3760,10的書籍，因此沒有聯合記錄中的第二個查詢。可能是我無法清除這裏的情況，但如果你對情況有所瞭解，你會明白我的觀點。

SELECT * FROM ( 
SELECT * FROM (
SELECT viewcount, b.isbn, booktitle, stock_status, price, description FROM book AS b 
INNER JOIN bookvisit AS bv ON b.isbn = bv.isbn WHERE b.price <> 0 AND hcategoryid = '25' 
ORDER BY viewcount DESC 
LIMIT 10, 10 
) AS t1 
UNION 
SELECT * FROM 
( 
SELECT viewcount, b.isbn, booktitle, stock_status, price, description FROM book AS b 
LEFT JOIN bookvisit AS bv ON b.isbn = bv.isbn WHERE b.price <> 0 AND hcategoryid = '25' 
AND viewcount IS NULL 
ORDER BY viewcount DESC 
LIMIT 10, 10 
) AS t2 
) 
    AS qry 
    ORDER BY viewcount DESC 
LIMIT 10 

Answer 1

不要對單獨的查詢使用限制。僅在最後使用限制。您希望從2個查詢中獲得洞結果集，然後僅顯示您需要的10個結果，無論這是限制0,10還是極限3760,10

SELECT * FROM ( 
SELECT * FROM ( 
    SELECT viewcount, b.isbn, booktitle, stock_status, price, description FROM book AS b 
    INNER JOIN bookvisit AS bv ON b.isbn = bv.isbn WHERE b.price <> 0 AND hcategoryid = '25' 
    ORDER BY viewcount DESC 
) AS t1 
UNION 
SELECT * FROM 
( 
    SELECT viewcount, b.isbn, booktitle, stock_status, price, description FROM book AS b 
    LEFT JOIN bookvisit AS bv ON b.isbn = bv.isbn WHERE b.price <> 0 AND hcategoryid = '25' 
    AND viewcount IS NULL 
    ORDER BY viewcount DESC 
) AS t2 
) 
AS qry 
ORDER BY viewcount DESC 
LIMIT 10, 10