当可以在两个表中进行搜索时，从相关的MySQL表中检索相关信息的有效查询是什么？

Question

I have two MySQL tables like below, and I use php to run my queries;

table_a

+--------+--------+--------+--------+
| taf1   | taf2   | taf3   | taf4   |
+========+========+========+========+
| dataa1 | dataa2 | dataa3 | dataa4 |
+--------+--------+--------+--------+
| datab1 | datab2 | datab3 | datab4 |
+--------+--------+--------+--------+
| datac1 | datac2 | datac3 | datac4 |
+--------+--------+--------+--------+
| datad1 | datad2 | datad3 | datad4 |
+--------+--------+--------+--------+

table_b

+--------+--------+--------+--------+
| tbf1   | tbf2   | tbf3   | tbf4   |
+========+========+========+========+
| dataa5 | dataa6 | dataa7 | dataa4 |
+--------+--------+--------+--------+
| datab5 | datab6 | datab7 | datab4 |
+--------+--------+--------+--------+
| datac5 | datac6 | datac7 | datac4 |
+--------+--------+--------+--------+
| datad5 | datad6 | datad7 | datad4 |
+--------+--------+--------+--------+

taf1 , taf2 , taf3 , and taf4 are fields of first table, and tbf1 , tbf2 , tbf3 , and tbf4 are fields of second table. taf4 and tbf4 have same entries, to link between the two tables. In the results page, I display taf1 , taf2 , taf3 and tbf1 fields. Also, search can be made in these 4 fields (a dropdown is given so that user can select search field). How can I do this?

Currently, I use the following code;

$key = "keyword";
$field = "fieldname";

if($field == "tbf1"){
  $engine = "table_b";
  //search in table_b. code incomplete.
}else{

  $query = "SELECT * FROM table_a WHERE $field LIKE '%$key%'";
  $result = mysql_query($query);
  while($row = mysql_fetch_array($result)){
    $link = $row['taf4'];
    $query2 = "SELECT NUMBER FROM table_b WHERE tbf4 = '$link'";
    $result2 = mysql_query($query2);
    $row2 = mysql_fetch_array($result2);
    echo $row['taf1']." - ".$row['taf2']." - ".$row['taf3']." - ".$row2['tbf1']."<br />";
  }

}

Is there any simple and effective method to do this?

Answer 1

SELECT taf.*,
       tbf.*
  FROM table_a taf
 INNER JOIN table_b tbf
         ON tbf.tbf4 = taf.taf4
 WHERE taf......