Question

我想在不同的数据库表中搜索数据？

例如，我输入一个单词，如'demo'，点击'搜索'按钮，然后显示数据与'产品'表和'文章'表中的'demo'字相关。

那么，我该如何编写sql语句？

顺便说一句，我使用PHP和Mysql。

Answer 1

您可以从查询开始它不适用于你，因为你没有显示你的表结构，列的任何信息。所以下面只是我的猜测

SELECT * FROM article a 
INNER JOIN product p
ON p.id = a.product_id
WHERE 
a.article LIKE "%demo%" 
OR
p.title LIKE "%demo%";

您可以尝试UNION ALL

SELECT * FROM article a 
a.article LIKE "%demo%" 

UNION ALL

SELECT * FROM product p 
p.title LIKE "%demo%";

但请确保它们应具有相同数量的列。阅读更多关于UNION here

的信息

下面是我开始学习它的工作原理的小代码

<?php
    mysql_connect("localhost", "root", "") or die("Error connecting to database: ".mysql_error());
    /*
        localhost - it's location of the mysql server, usually localhost
        root - your username
        third is your password

        if connection fails it will stop loading the page and display an error
    */

    mysql_select_db("your_database") or die(mysql_error());
    /* your_database is the name of database we've created */
?>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
    <title>Search results</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <link rel="stylesheet" type="text/css" href="style.css"/>
</head>
<body>
<?php
    $query = $_GET['query']; 
    // gets value sent over search form and in your case it is demo

    $min_length = 3;
    // you can set minimum length of the query if you want

    if(strlen($query) >= $min_length){ // if query length is more or equal minimum length then

        $query = htmlspecialchars($query); 
        // changes characters used in html to their equivalents, for example: < to &gt;

        $query = mysql_real_escape_string($query);
        // makes sure nobody uses SQL injection

        $raw_results = mysql_query("SELECT * FROM article a INNER JOIN product p
                  ON p.id = a.product_id WHERE (`title` LIKE '%".$query."%') OR (`text`  LIKE '%".$query."%')") or die(mysql_error());

        // * means that it selects all fields, you can also write: `id`, `title`, `text`
        // articles is the name of our table

        // '%$query%' is what we're looking for, % means anything, for example if $query is Hello
        // it will match "demo", "here demo", "demohere", if you want exact match use `title`='$query'
        // or if you want to match just full word so "gogohello" is out use '% $query %' ...OR ... '$query %' ... OR ... '% $query'

        if(mysql_num_rows($raw_results) > 0){ // if one or more rows are returned do following

            while($results = mysql_fetch_array($raw_results)){
            // $results = mysql_fetch_array($raw_results) puts data from database into array, while it's valid it does the loop

                echo "<p><h3>".$results['title']."</h3>".$results['text']."</p>";
                // posts results gotten from database(title and text) you can also show id ($results['id'])
            }

        }
        else{ // if there is no matching rows do following
            echo "No results";
        }

    }
    else{ // if query length is less than minimum
        echo "Minimum length is ".$min_length;
    }
?>
</body>
</html>

如何在不同的数据库表中搜索数据？

1 个答案: