Question

我可以显示产品列表，但我想从view_product表中不显示产品的观看次数

product_tbl表

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pro_id  |  product  | description  
----------------------------------
1       |  prodcut1 | description 
----------------------------------
2       |  prodcut2 |  description 
----------------------------------
3       |  prodcut3 |  description 
----------------------------------

view_product表

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view_id |  username  | product  | view_time 
------------------------------------------
1       |  usename1 | prodcut1 | 2019-10-31 11:45:00 
------------------------------------------
2       |  usename2 | prodcut1 |2019-10-31 11:46:00
------------------------------------------
3       |  usename2 | prodcut1 |2019-10-31 11:45:00 
------------------------------------------
4       |  usename1 | prodcut1 |2019-10-31 11:46:00
------------------------------------------

$stmt = $conn->prepare("Select pro_id,product, description,qty from product_tbl");
$stmt->execute();
$row = $stmt-> fetchAll(PDO::FETCH_ASSOC);
$user_arr=array('data'=>$row);
echo json_encode($user_arr);

基于product_id，我想从view_product表和空值行中查看每个产品的计数（如果未查看产品），如何在PDO json编码中使用以下查询。

select count(id) as count1 from view_product where user_id=".$row['pro_id'].";

预期输出如下

------------------------------------------------
pro_id  |  product  | description  | view count
------------------------------------------------
1       |  prodcut1 | description  | 2
------------------------------------------------
2       |  prodcut2 |  description | 2
------------------------------------------------
3       |  prodcut3 |  description | NULL
------------------------------------------------

Answer 1

避免使用n + 1个查询，而应将join语句与count()函数结合使用，并在最后将它们按列分组。

SELECT 
  p.prod_id, 
  p.product, 
  p.description,
  COUNT(v.view_id) AS view_count
FROM product_tbl AS p
LEFT JOIN view_product AS v ON p.product = v.product
GROUP BY v.product

PDO json_encode中的观看者计数

1 个答案: