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MySQL Tutorial - Query Multiple Tables Jointly

By: FYIcenter.com

(Continued from previous topic...)

How To Query Multiple Tables Jointly?

If you want to query information stored in multiple tables, you can use the SELECT statement with a WHERE condition to make an inner join. Assuming that you have 3 tables in a forum system: "users" for user profile, "forums" for forums information, and "posts" for postings, you can query all postings from a single user with a script as shown below:

<?php
  include "mysql_connection.php";

  $userID = 101;
  $sql = "SELECT posts.subject, posts.time, users.name,
    . " forums.title"
    . " FROM posts, users, forums"
    . " WHERE posts.userID = ".$userID
    . " AND posts.userID = users.id"
    . " AND posts.forumID = forums.id";
  $rs = mysql_query($sql, $con);
  while ($row = mysql_fetch_assoc($rs)) {
    print($row['subject'].", ".$row['time'].", "
      .$row['name'].", ".$row['title']."\n");
  }
  mysql_free_result($rs);

  mysql_close($con); 
?>

(Continued on next topic...)

1. How To Create a New Table?
2. How To Get the Number of Rows Selected or Affected by a SQL Statement?
3. How To Insert Data into an Existing Table?
4. How To Fix the INSERT Command Denied Error?
5. How To Insert Multiple Rows with a SELECT Statement?
6. What Is a Result Set Object?
7. How To Query Tables and Loop through the Returning Rows?
8. How To Break Query Output into Pages?
9. How To Update Existing Rows in a Table?
10. How To Delete Existing Rows in a Table?
11. How To Quote Text Values in SQL Statements?
12. How To Quote Date and Time Values in SQL Statements?
13. How To Display a Past Time in Days, Hours and Minutes?
14. How To Perform Key Word Search in Tables?
15. How To Build WHERE Criteria with Web Form Search Fields?
16. How To Query Multiple Tables Jointly?
17. How To Define the ID Column as Auto-Incremented?
18. How To Get the Last ID Assigned by MySQL?