php - How can I connect a value of one mySQL table to a value of another table? -

i have 2 tables in mysql database:

table "animals":

|   animal   |    name     |  |:-----------|------------:| |    cat     |     tom     |  |    dog     |             |    

table "orders":

|     id     |   animal    |  |:-----------|------------:| |      1     |     cat     |  |      2     |     dog     |   

at first select table "orders" following data:

    <?php      $pdo = database::connect();     $sql = 'select * orders order id asc';     foreach ($pdo->query($sql) $row) {      echo ('<td>a:'.$row['id'].'</td>');          echo ('<td>b:'.$row['animal'].'</td>');      echo ('<td>c:'.$row['animal'].'</td>');               }     database::disconnect();     ?> 

now want check if in mysql table "animal" animal has name. if yes print @ position b name. if there no name print animal:

|      a:1     |     b:tom     |      c:cat     |  |      a:2     |     b:dog     |      c:dog     |  

---

thank answers! tried work answer of jayo2k. need little change in question, found out did little mistake. here try describe need specific possible:

table "animals":

|   name     |   animal    |  |:-----------|------------:| |    tom     |     cat     |  |   jerry    |     dog     |    |   alfred   |    duck     |   |    sam     |             |  |   donald   |             |   

table "orders":

|     id     |   animal    |  |:-----------|------------:| |      1     |     cat     |  |      2     |     dog     | |      3     |     duck    | |      4     |     frog    | |      5     |     pig     | 

with following code jayo2k...

    <?php      $pdo = database::connect();     $sql = "select * animals, orders orders.animal = animals.animal";     foreach ($pdo->query($sql) $row) {      echo '<tr> ';     echo('<td>a:'.$row['id'].' </td>');     echo('<td>a:'.$row['animal'].' </td>');     echo('<td>b:'.$row['name'].' </td>');     echo '</tr> ';      }     database::disconnect();     ?>       

... result:

|      a:1     |     b:cat     |      c:tom     |  |      a:2     |     b:dog     |      c:jerry   | |      a:3     |     b:duck    |      c:alfred  | 

but need is:

|      a:1     |     b:cat     |      c:tom     |  |      a:2     |     b:dog     |      c:jerry   | |      a:3     |     b:duck    |      c:alfred  | |      a:4     |     b:frog    |      c:frog    | |      a:5     |     b:pig     |      c:pig     | 

you can use left join, , use if condition check value not empty, along ifnull, make null values in columns blank.

select o.id, if(ifnull(a.name, '') = '', a.animal, a.name) name,  a.animal orders o left join animals      on o.animal = a.animal order o.id desc