通过PHP查询从mysql表打印值的最佳方法

Question

Most of the times in my pages, I need to print the value of only one field in the table, by using a loop. For example:

 <?php

 for($i=1;$i<=mysql_num_rows($result);$i++)
 {
     echo $row['name'];
     $sql1="select industry from table_industry where profid='".$row['prof']."'";
     $result1=mysql_query($sql1);
     $row1=mysql_fetch_array($result1);
     echo $row1['industry']; ?>
 }
 ?>

For example, I have 5000+ record in table and the above loop will execute 5000+ times.

What would be the best way to print the value of the industry field from the table table_industry ?

Is it the code I wrote above, or is there a method for faster execution?

Answer 1

1. Avoid looping over all 5000 records. Use a filtering or pagination
2. Even more avoid nested queries. Use power of JOIN .

Answer 2

My best guess is that JOIN will help you out here.

With join you can instruct he MySQL server to combine different tables and access them in a single query, for example:

SELECT
  table_prof.profid
, table_prof.name
, table_industry.industry 
FROM table_prof
JOIN table_industry USING ( profid )
ORDER BY table_prof.name ASC;

Generally speaking, querying the database in a loop is a very bad idea and should be avoided unless you know exactly why you are doing it. Querying in a loop can easily bring a database server to it's knees.

Answer 3

use JOIN

if you want to include only those rows with values in industry table then sql will be

    SELECT 
     table_prof.profid 
    , table_prof.name 
    , table_industry.industry  
      FROM table_prof 
      JOIN table_industry USING ( profid ) 
      ORDER BY table_prof.name ASC;

and if you want to include all values from table table_prof then sql will be

      SELECT 
     table_prof.profid 
    , table_prof.name 
    , table_industry.industry  
      FROM table_prof 
      LEFT JOIN table_industry USING ( profid ) 
      ORDER BY table_prof.name ASC;

i think this will help you...

Answer 4

为了遵循您的逻辑，我将选择所有信息，将其加载到哈希中并在哈希中进行迭代，而不是杀死数据库。