SQL変数で動作しないPHP変数

Question

PHPとSQLに関しては初心者ですので、私を許してください。 tblEmployees.Workgroupの変数を渡すときに私のSQL文がうまくいかない理由を理解しようとしています。私は "CS Lead"と変数を入れたとき、それは完璧に動作します。他の情報を含める必要がある場合はお知らせください。ありがとう！

<?php 
include 'header.php'; //Include header 
include 'sidebar.php'; //Include sidebar 

$workgroup = 'CS Lead'; 

$stmt = $db->query("SELECT 
        tblSchedule.CurrentSchedule, 
        tblSchedule.Login, 
        tblSchedule.StartTime, 
        tblSchedule.EndTime, 
        tblSchedule.Sunday, 
        tblSchedule.Monday, 
        tblSchedule.Tuesday, 
        tblSchedule.Wednesday, 
        tblSchedule.Thursday, 
        tblSchedule.Friday, 
        tblSchedule.Saturday, 
        tblSchedule.Lunch_Start, 
        tblSchedule.Lunch_End, 
        tblSchedule.Brk1_Start, 
        tblSchedule.Brk1_End, 
        tblSchedule.Brk2_Start, 
        tblSchedule.Brk2_End, 
        tblSchedule.Brk3_Start, 
        tblSchedule.Brk3_End, 
        tblSchedule.Lunch2_Start, 
        tblSchedule.Lunch2_End, 
        tblSchedule.TM_Day, 
        tblSchedule.TM_Start, 
        tblSchedule.TM_End, 
        tblEmployees.Workgroup 
       FROM tblSchedule 
       LEFT JOIN tblEmployees 
       ON tblSchedule.Login=tblEmployees.Login 
       WHERE CurrentSchedule='Y' AND tblEmployees.Workgroup = ' . $workgroup . ' 
       LIMIT 100"); 

$stmt -> execute(); 
?> 

Answer 1

二重引用符を使用...

$stmt = $db->query("SELECT 
        tblSchedule.CurrentSchedule, 
        tblSchedule.Login, 
        tblSchedule.StartTime, 
        tblSchedule.EndTime, 
        tblSchedule.Sunday, 
        tblSchedule.Monday, 
        tblSchedule.Tuesday, 
        tblSchedule.Wednesday, 
        tblSchedule.Thursday, 
        tblSchedule.Friday, 
        tblSchedule.Saturday, 
        tblSchedule.Lunch_Start, 
        tblSchedule.Lunch_End, 
        tblSchedule.Brk1_Start, 
        tblSchedule.Brk1_End, 
        tblSchedule.Brk2_Start, 
        tblSchedule.Brk2_End, 
        tblSchedule.Brk3_Start, 
        tblSchedule.Brk3_End, 
        tblSchedule.Lunch2_Start, 
        tblSchedule.Lunch2_End, 
        tblSchedule.TM_Day, 
        tblSchedule.TM_Start, 
        tblSchedule.TM_End, 
        tblEmployees.Workgroup 
       FROM tblSchedule 
       LEFT JOIN tblEmployees 
       ON tblSchedule.Login=tblEmployees.Login 
       WHERE CurrentSchedule='Y' AND tblEmployees.Workgroup = '$workgroup' 
       LIMIT 100"); 

OR

WHERE CurrentSchedule='Y' AND tblEmployees.Workgroup = {$workgroup}