Comparing two SQL results from two tables in Javascript

I have created a (very lengthy) way of comparing two results from two different tables in JS. I would like it that if the name entered in the lates table does not exist in the student table already, then it is deleted immediately. The problem lies in the getlist function I believe.

I know this is a terrible way of doing what I need, but this is the way it needs to be done for the moment.

<fieldset>
        <legend><b>Details</b></legend>
        <label>First Name </label><input id = "firstname" type="text" autofocus="" placeholder="Enter first name"><br><br>
        <label>Last Name </label><input id = "lastname" type="text" autofocus="" placeholder="Enter last name"><br><br>
    </fieldset>

    <fieldset>
        <legend><b>Information</b></legend>
        <label> Current date:</label>
        <input type="text" id="datelate"/><br><br>
        <label> Detention date:</label>
        <input id = "detentiondate" type="date" ><br><br>
        <label>Time</label>
            <select id="mora">
                <option value="AM">Morning</option>
                <option value="PM">Afternoon</option>
            </select>
        <br> <br>
        <label> Reason:</label>
        <textarea id = "reason" rows="2" cols="60"></textarea><br><br>
    </fieldset>

    <br>
    <input type="reset" value="Reset">

    <button type="button" id="addlate" onclick="addLate(); searchlastname2(); searchlastnameStudent();">Add late</button>

    <p id="list2"></p>
    <p id="list3"></p>

    </body>

<script>

if (window.openDatabase) {
    var mydb = openDatabase("students2_db", "0.1", "A Database of Students", 1024 * 1024);

    mydb.transaction(function (t) {
         t.executeSql("CREATE TABLE IF NOT EXISTS student (id INTEGER PRIMARY KEY ASC, fname TEXT, lname TEXT, mclass TEXT, aclass TEXT, com TEXT, lates INTEGER DEFAULT 0)");
         t.executeSql("CREATE TABLE IF NOT EXISTS lates (lid INTEGER PRIMARY KEY ASC, flname TEXT, llname TEXT, time TEXT, reason TEXT, date TEXT, nextdet TEXT)");
    });

} else {
    alert("WebSQL is not supported by your browser!");
}


function updateList2(transaction, results) {
    var listitems = "";
    var listholder = document.getElementById("list2");
    listholder.innerHTML = "";

    var i;

    for (i = 0; i < results.rows.length; i++) {

        var row = results.rows.item(i);

    var llname = row.llname; }

    getlist(llname);

}

function updateList3(transaction, results) {

    var listitems = "";
    var listholder = document.getElementById("list3");
    listholder.innerHTML = "";

    var i;

    for (i = 0; i < results.rows.length; i++) {

        var row = results.rows.item(i);

        var lname = row.llname; }

        getlist(lname);

}


function getlist(lname,llname){

if (lname != llname) {
        mydb.transaction(function (t) {
            t.executeSql("DELETE FROM lates WHERE llname = ?", [llname]);
            });
    }
}


function searchlastname2() {
    var llname = document.getElementById("lastname").value;

    if (mydb) {

        mydb.transaction(function (t) {
            t.executeSql("SELECT DISTINCT llname FROM lates WHERE llname =?", [llname], updateList2);
        });
    } else {
        alert("db not found, your browser does not support web sql!");
    }
}

function searchlastnameStudent() {
    var lname = document.getElementById("lastname").value;

    if (mydb) {

        mydb.transaction(function (t) {
            t.executeSql("SELECT DISTINCT lname FROM student WHERE lname =?", [lname], updateList3);
        });
    } else {
        alert("db not found, your browser does not support web sql!");
    }
}


function ClearFunction() {
    document.getElementById("mora").value = "";
}

function DateFunction() {
    var today = new Date();
    var dd = today.getDate();
    var mm = today.getMonth()+1; //January is 0!
    var yyyy = today.getFullYear();

    if(dd<10) {
        dd='0'+dd
    } 

    if(mm<10) {
        mm='0'+mm
    } 

    today = dd+'-'+mm+'-'+yyyy;
    document.getElementById('datelate').value= today;
}

function addLate() {

    if (mydb) {

        var flname = document.getElementById("firstname").value;
        var llname = document.getElementById("lastname").value;
        var date = document.getElementById("datelate").value;
        var nextdet = document.getElementById("detentiondate").value;
        var time = document.getElementById("mora").value;
        var reason = document.getElementById("reason").value;

        if (flname !== "" && date !== "" && nextdet !== "" && llname !== "" && reason !== "" && time !== "") {

            mydb.transaction(function (t) {
                t.executeSql("INSERT INTO lates (flname,llname,time,reason,date,nextdet) VALUES (?,?,?,?,?,?)" , [flname,llname,time,reason,date,nextdet]);
                t.executeSql("UPDATE student SET lates = lates + 1 WHERE lname =? ", [llname]);
                alert("Entry succesfully added");
                document.getElementById("firstname").value = "";
                document.getElementById("lastname").value = "";
                document.getElementById("detentiondate").value = "";
                document.getElementById("reason").value = "";
            });
        } else {
            alert("You must fill out all the empty information!");
        }
    } else {
        alert("db not found, your browser does not support web sql!");
    }
}


</script>