SQL Query not Giving a Result

Question

I am trying to login my user and i need to search whether the user exists in the db or not. My db is ClearDB using MySQL on Heroku. I am using node.js. This is my code:

if (req.body.isAdmin === 1) {
      connection.query(
        `SELECT * FROM admin WHERE username='${req.body.username}' AND password='${req.body.password}'`,
        function (err, rows) {
          if (!err) {
            console.log(rows);
            res.status(201).json({
              success: true,
              message: "Admin Logged In!",
            });
          } else {
            res
              .status(404)
              .json({ success: false, message: "Admin Not Found!" });
          }
        }
      );
    } else {
      connection.query(
        `SELECT * FROM guard WHERE username='${req.body.username}' AND password='${req.body.password}'`,
        function (err, rows) {
          if (!err) {
            console.log(rows);
            res.status(201).json({
              success: true,
              message: "Guard Logged In!",
            });
          } else {
            res
              .status(404)
              .json({ success: false, message: "Guard Not Found!" });
          }
        }
      );
    }
  } catch (error) {
    res.status(500);
    throw new Error(error);
  }

In the above code, i first check whether the user is an admin or not, then i execute the respective query. The db connects properly i.e., there is no issue with the db connection.

The issue is that there is no output for any of the queries i.e., rows variable is empty. Even if the data is false and doesn't match the data available, it doesn't give an error and also doesn't give an output. I have double-checked the connection and the query and they seem fine. I don't get where the issue is. Please help!