Advanced SQL Query Challenges with Solutions
Database Schema
CREATE TABLE learners(
learner_id VARCHAR(10),
full_name VARCHAR(10),
birth_date DATETIME,
gender VARCHAR(10)
);
INSERT INTO learners VALUES
('01', 'Zhao Lei', '1990-01-01', 'Male'),
('02', 'Qian Dian', '1990-12-21', 'Male'),
('03', 'Sun Feng', '1990-05-20', 'Male'),
('04', 'Li Yun', '1990-08-06', 'Male'),
('0 ...
Posted on Sat, 26 Sep 2026 16:52:42 +0000 by erupt
Advanced Django ORM Query Techniques: Multi-Table Operations, Aggregation, and Complex Filtering
Foreign Key Relaitonships and CRUD Operations
One-to-Many Relationships
# Create operation with direct foreign key reference
Book.objects.create(title='Analects', price=899.23, publisher_id=1)
# Create using related object
publisher_instance = Publisher.objects.get(id=2)
Book.objects.create(title='Dream of the Red Chamber', price=666.23, publi ...
Posted on Tue, 01 Sep 2026 16:29:29 +0000 by parthatel
Essential MySQL Commands for Database Operations
Database Operations
SHOW DATABASES;
USE database_name;
CREATE DATABASE [IF NOT EXISTS] db_name;
DROP DATABASE [IF EXISTS] db_name;
SHOW CREATE DATABASE db_name;
ALTER DATABASE db_name CHARACTER SET charset_name;
Tible Creatoin Examples
DROP TABLE IF EXISTS user_main;
CREATE TABLE `user_main` (
`user_id` varchar(10) NOT NULL,
`login_name` var ...
Posted on Sun, 23 Aug 2026 16:49:27 +0000 by vanderlay
Efficient Multiple Count Queries in MySQL
Performing Multiple Count Operations in MySQL
Database Connection Setup
import mysql.connector
db_connection = mysql.connector.connect(
host="db_server",
user="db_user",
password="secure_password",
database="inventory_db"
)
Executing Count Queries
db_cursor = db_connection.cursor()
# Count prod ...
Posted on Sat, 20 Jun 2026 17:41:51 +0000 by jdc44
Advanced SQL Query Challenges: 15 Practical Problems and Solutions
SELECT COUNT(instructor_id) FROM instructors WHERE instructor_name LIKE 'Li%';
This query counts the number of instructors whose last name starts with "Li" by using the LIKE operator with a wildcard pattern.
Problem 2: Find students who scored higher in course "01" than in course "02"
SELECT st.student_id, crs1.s ...
Posted on Tue, 19 May 2026 08:52:00 +0000 by sarakmo