Question

如何使用COUNT关键字计算此查询的结果？

SELECT COUNT (*)返回错误的结果。

SELECT files.* FROM files
LEFT JOIN tags_files ON tags_files.id_file = files.id
LEFT JOIN tags ON tags.id = tags_files.id
WHERE tags.name LIKE '%search%' OR files.name LIKE '%search%'

Answer 1

如果要计算结果，请尝试以下查询：

SELECT COUNT( files.id ) AS total_num FROM files
LEFT JOIN tags_files ON tags_files.id_file = files.id
LEFT JOIN tags ON tags.id = tags_files.id
WHERE tags.name LIKE '%search%' OR files.name LIKE '%search%'

Answer 2

您可以使用rowCount或num_rows取决于您使用的内容，因此它只会计算查询返回的行数

示例：

<?php 
    //For PDO
    $sel = $dbh->prepare("SELECT files.* FROM files LEFT JOIN tags_files ON   tags_files.id_file = files.id LEFT JOIN tags ON tags.id = tags_files.id WHERE tags.name LIKE '%search%' OR files.name LIKE '%search%'");
    $sel->execute();
    $count = $sel->rowCount();
  
    //For mysqli
    $sel = "SELECT files.* FROM files LEFT JOIN tags_files ON   tags_files.id_file = files.id LEFT JOIN tags ON tags.id = tags_files.id WHERE tags.name LIKE '%search%' OR files.name LIKE '%search%'";
    $result = mysqli_query($con,$sel);
    $count = mysqli_num_rows($result);
?>

如何计算查询结果

2 个答案: