Pagination of MySQL rows in Treeview

Code Explanation: Breaking Down the Activities

1. Importing Required Modules

from tkinter import ttk
import tkinter as tk
from sqlalchemy import create_engine, text

• ttk: Provides advanced widgets like Treeview.
• create_engine: Establishes a connection with the database.
• text: Allows executing parameterized SQL queries.

2. Setting Up the Database Connection

my_conn = create_engine("mysql+mysqldb://root:test@localhost/my_tutorial")
my_conn = my_conn.connect()  # Establish the connection to MySQL

• my_conn: This is the connection object used to execute SQL queries.

3. Fetching Total Number of Records

r_set = my_conn.execute(text("SELECT count(*) as no from STUDENT"))
data_row = r_set.fetchone() 
no_rec = data_row[0]  # Total number of rows in the table
limit = 5  # Number of records to display per page

• no_rec: Holds the total number of records in the student table.
• limit: Controls how many rows are displayed per page.

4. Setting Up the Tkinter Window

my_w = tk.Tk()  # Create the main window
my_w.geometry("400x400")  # Set window dimensions
my_str = tk.StringVar()  # For displaying query information

• my_w: The main window for the application.
• my_str: A string variable used to display the current SQL query.

5. Defining the Function to Display Data

def my_display(offset):
    trv = ttk.Treeview(my_w, selectmode='browse')
    trv.grid(row=1, column=2, padx=20, pady=20, columnspan=3)
    ...

• This function dynamically fetches and displays rows from the database in the Treeview widget.
• offset: Determines the starting row for the SQL query.

6. Creating the Treeview Widget

trv['columns'] = ('1', '2', '3', '4', '5')
trv['show'] = 'headings'
trv.column('1', width=30, anchor='c')
trv.column('2', width=80, anchor='w')
trv.heading('1', text='id')
trv.heading('2', text='Name')
...

• The Treeview widget is configured with columns for ID, Name, Class, Mark, and Gender.

7. Fetching Data for the Current Page

# q = "SELECT * from student LIMIT " + str(offset) + "," + str(limit)
q = "SELECT * FROM student LIMIT :offset , :limit"
r_set = my_conn.execute(text(q), {'offset': offset, 'limit': limit})

# Adding rows to Treeview
for dt in r_set:
    trv.insert("", 'end', iid=dt[0], text=dt[0],
               values=(dt[0], dt[1], dt[2], dt[3], dt[4]))

• q: Constructs the SQL query with the current offset and limit by using parameterized query.
• Rows are fetched and added to the Treeview widget using the insert method.

8. Enabling and Disabling Navigation Buttons

back = offset - limit
next = offset + limit
b1 = tk.Button(my_w, text='< Prev', command=lambda: my_display(back))
b1.grid(row=2, column=2, sticky='E')
b2 = tk.Button(my_w, text='Next >', command=lambda: my_display(next))
b2.grid(row=2, column=3)

if(no_rec <= next): 
    b2['state'] = 'disabled'  # Disable Next button
else:
    b2['state'] = 'active'  # Enable Next button

if(back >= 0):
    b1['state'] = 'active'  # Enable Prev button
else:
    b1['state'] = 'disabled'  # Disable Prev button

• The Next button is disabled if we are on the last page of records.
• The Previous button is disabled if we are on the first page.

9. Displaying Query Information

my_str.set(q + '\nnext: ' + str(next) + "\n back:" + str(back))
l1 = tk.Label(my_w, textvariable=my_str)
l1.grid(row=3, column=1, columnspan=3)

• The label dynamically displays the SQL query and pagination details.

from tkinter import ttk
import tkinter as tk
from sqlalchemy import create_engine,text
my_conn = create_engine("mysql+mysqldb://root:test@localhost/my_tutorial")
my_conn=my_conn.connect() # database connection object or connection string
###### end of connection ####
r_set=my_conn.execute(text("SELECT count(*) as no from STUDENT"))
data_row=r_set.fetchone() 
no_rec=data_row[0] # Total number of rows in table
limit = 5; # No of records to be shown per page or view.
##### tkinter window ######
from tkinter import ttk
import tkinter  as tk 
my_w = tk.Tk()
my_w.geometry("400x400") # width and height of the window
my_str = tk.StringVar() # to display query at end
def my_display(offset):    
    ###
    trv = ttk.Treeview(my_w, selectmode ='browse')
  
    trv.grid(row=1,column=2,padx=20,pady=20,columnspan=3)
# number of columns
    trv["columns"] = ("1", "2", "3","4","5")
  
# Defining heading
    trv['show'] = 'headings'
  
# width of columns and alignment 
    trv.column("1", width = 30, anchor ='c')
    trv.column("2", width = 80, anchor ='w')
    trv.column("3", width = 80, anchor ='c')
    trv.column("4", width = 80, anchor ='c')
    trv.column("5", width = 80, anchor ='c')
  
# Headings  
# respective columns
    trv.heading("1", text ="id")
    trv.heading("2", text ="Name")
    trv.heading("3", text ="Class")
    trv.heading("4", text ="Mark")  
    trv.heading("5", text ="Gender")
    ###
    #q="SELECT * from student LIMIT "+ str(offset) +","+str(limit)
    q="SELECT * FROM student LIMIT :offset , :limit"
    r_set=my_conn.execute(text(q),{'offset':offset,'limit':limit})
    # Adding rows to Treeview 
    for dt in r_set: 
        trv.insert("", 'end',iid=dt[0], text=dt[0],
               values =(dt[0],dt[1],dt[2],dt[3],dt[4]))

    # Show buttons for navigation to different pages or views 
    back = offset - limit # This value is used by Previous button
    next = offset + limit # This value is used by Next button       
    b1 = tk.Button(my_w, text='< Prev', command=lambda: my_display(back))
    b1.grid(row=2,column=2,sticky='E')
    b2 = tk.Button(my_w, text='Next >', command=lambda: my_display(next))
    b2.grid(row=2,column=3)

    if(no_rec <= next): 
        b2["state"]="disabled" # disable next button
    else:
        b2["state"]="active"  # enable next button
        
    if(back >= 0):
        b1["state"]="active"  # enable Prev button
    else:
        b1["state"]="disabled"# disable Prev button 
    # for your understanding of how the offset value changes
    # query is displayed here, it is not part of the script 
    my_str.set(q + '\n' + "next: " + str(next) + "\n back:"+str(back))
    l1 = tk.Label(my_w, textvariable=my_str)
    l1.grid(row=3,column=1,columnspan=3)
my_display(0)  # for the first or default view offset is set to 0       
my_w.mainloop()

Subhendu Mohapatra

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