选择使用jquery使用单选按钮查询多个表

I'm building a comics website, which has two subsites: Comics and Artwork. Comics and Artwork are stored in two separate tables.

I have a search function that allows the user to search for an image.

I'd like to give them an option to choose to search for only comics, only artwork, or both.

I have the following javascript which I believe should be working:

    <script type="text/javascript">

        function search(searchString) {     
           var site = $("#site").val();
           $.get("./scripts/search.php", {_input : searchString, _site : site},
                function(returned_data) {
                    $("#output").html(returned_data);
                }
            );
        }

        function searchChoice(choice) {     
           $.get("./scripts/search.php", {_choice : choice}
           );
        }

</script>

And the following HTML:

    <!--Search filtering for comics, artwork, or both-->
<span class="search"><b>Search for: </b> </span>

<div class="btn-group" data-toggle="buttons-radio">
<span class="search">
    <button type="button" class="btn" id="comics" onclick="searchChoice(this.id)">Comics</button> 
    <button type="button" class="btn" id="artwork" onclick="searchChoice(this.id)">Artwork</button> 
    <button type="button" class="btn" id="all" onclick="searchChoice(this.id)">All</button> 
</span>
</div>

<br/>
<br/>

<!--Search functionality-->
<span class="search">
    <input type="text" onkeyup="search(this.value)" name="input" value="" />
    <input id="site" type="hidden" value="<?php echo $site; ?>">
</span>

<br />
<span id="output"><span class="sidebarimages">  </span></span>

My question is here with the PHP in querying TWO tables:

Am I doing the JOIN correctly?

$input = (isset($_GET['_input']) ? ($_GET['_input']) : 0); 
$choice = (isset($_GET['_choice']) ? ($_GET['_choice']) : "all");
$site = (isset($_GET['site']) ? ($_GET['site']) : null);


if ($choice == "artwork") {
    $sql = "SELECT id, title, thumb FROM artwork";
    $thumbpath = "./images/Artwork/ArtThumbnails/";
}
else if ($choice == "comics") {
    $sql = "SELECT id, title, thumb FROM comics";
    $thumbpath = "./images/Comics/ComicThumbnails/";
}
else {
    $sql = "SELECT id, title, thumb FROM comics 
            UNION 
            SELECT id, title, thumb FROM artwork";
    $thumbpath = "./images/AllThumbnails/";
}


$imgpaths = $mysqli->query($sql);
mysqli_close($mysqli);

Thanks!

No, you're not stating any conditions for joining the 2 tables, also in the case of looking in both tables, you may want to consider using UNION instead, as in:

SELECT * FROM comics
UNION
SELECT * FROM artwork

To use JOIN function you need relations between tables (foreign keys connecting one to another)