Taking data from a database and putting into a table in a GUI

Tkinter doesn't provide a table widget on its own, but you can use grid and insert Labels in it. To get all the data from your database you just need to execute a query SELECT * FROM <Table> and with .fetchall() you get a list with the duble. This is your recordsclass:

class records():     #class created to see records that have been previously inputted#    def __init__(self,master):        self.master=master        self.master.geometry('250x200+100+200')        self.master.title('Records')        self.connection = sqlite3.connect('bmidatabase.db')        self.cur = self.connection.cursor()        self.dateLabel = Label(self.master, text="Date", width=10)        self.dateLabel.grid(row=0, column=0)        self.BMILabel = Label(self.master, text="BMI", width=10)        self.BMILabel.grid(row=0, column=1)        self.stateLabel = Label(self.master, text="Status", width=10)        self.stateLabel.grid(row=0, column=2)        self.showallrecords()    def showallrecords(self):        data = self.readfromdatabase()        for index, dat in enumerate(data):            Label(self.master, text=dat[0]).grid(row=index+1, column=0)            Label(self.master, text=dat[1]).grid(row=index+1, column=1)            Label(self.master, text=dat[2]).grid(row=index+1, column=2)    def readfromdatabase(self):        self.cur.execute("SELECT * FROM BMIStorage")        return self.cur.fetchall()

Since you've closed your connection to the database (which is a bug, because you cannot calculate another BMI), we need to open it again. After that we create a "header" with labels into the grid layout. Note here that we use grid on a seperate line. The reason for this is if we write self.ourLabel = Label().grid() we'll get a None back from the grid-method and can't use the reference for future purpose. So you will need to correct your other code. After that we fetch all data from the database and create 3 Labels for each row.