mysql - 我怎样才能压缩3个mysql查询；使用 AVG 和 COUNT

Question

这些查询是否可以压缩为 2 个，甚至更好为 1 个查询？

查询 1

$stmt = $conn->
prepare("
    SELECT providers.Provider_ID, providers.Description, reviews.Date, reviews.F_Name, reviews.S_Name, reviews.Website, reviews.Rating, reviews.Message, reviews.Email_Address
    FROM providers
    INNER JOIN reviews ON reviews.Provider=providers.Provider_ID    
    WHERE providers.Provider_ID LIKE CONCAT('%',:provider,'%') LIMIT $set_limit 
");
$stmt->bindParam(':provider', $provider, PDO::PARAM_STR);
$stmt->execute();
$rows = $stmt->fetchAll(PDO::FETCH_ASSOC);

查询 2

$stmt = $conn->
prepare("
    SELECT ROUND(AVG(rating),1) as AVG_Rating
    FROM reviews
    WHERE Provider LIKE CONCAT('%',:provider,'%') 
");
$stmt->bindParam(':provider', $provider, PDO::PARAM_STR);
$stmt->execute();
$get_average = $stmt->fetchColumn();    

查询3

$stmt = $conn->
prepare("
    SELECT COUNT(*)
    FROM reviews
    WHERE Provider LIKE CONCAT('%',:provider,'%') 
");
$stmt->bindParam(':provider', $provider, PDO::PARAM_STR);
$stmt->execute();
$total_rows = $stmt->fetchColumn();

Answer 1

您正在汇总不同粒度级别的结果。一个是提供者级别，另一个是审核级别。因此，您需要带有摘要信息的评论。您可以通过加入聚合结果来获得此结果:

SELECT p.Provider_ID, p.Description, r.Date, r.F_Name, r.S_Name,
       r.Website, r.Rating, r.Message, r.Email_Address,
       tsum.AVG_Rating, tsum.cnt
FROM providers p INNER JOIN
     reviews r
     ON r.Provider = p.Provider_ID CROSS JOIN
     (SELECT Provider, ROUND(AVG(rating),1) as AVG_Rating, COUNT(*) as cnt
      FROM reviews
      WHERE Provider LIKE CONCAT('%',:provider,'%')
     ) tsum
WHERE p.Provider_ID LIKE CONCAT('%',:provider,'%')
LIMIT $set_limit