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MongoDB Atomic Operations MongoDB does not support multi-document ACID transactions. Therefore, you must design your application logic to handle data consistency without relying on the database for cross-document integrity. However, MongoDB provides a comprehensive set of atomic operations for single-document modifications. An atomic operation ...

Redis Cache and Database Consistency Caching improves performance and reduces database load, but introduces potential inconsistencies between cached data and the database. Inconsistent data leads to stale reads from the cache. Non-Concurrency Scenarios Update Cache First, Then Database If cache udpate succeeds but database update fails, the cac ...

Prerequisites and Initial Setup Start with a minimal CentOS 7 environment to avoid conflicts. Create a temporary workspace for the installation bundle. mkdir -p /mysql cd /mysql wget https://cdn.mysql.com/archives/mysql-8.0/mysql-8.0.16-2.el7.x86_64.rpm-bundle.tar tar -xvf mysql-8.0.16-2.el7.x86_64.rpm-bundle.tar Cleaning Up Existing MariaDB o ...

1. String Concatenation Operator SELECT 'Employee: ' || ename || ', Role: ' || job || ', Salary: ' || sal AS details FROM emp; 2. Convert Strings to Lowercase SELECT LOWER(ename) AS lowercase_name FROM emp; 3. Value Replacmeent SELECT DECODE(deptno, 10, 'Development', 20, 'Product', 30, 'Maintenance') AS department FROM emp; 4. Extract Curre ...

Window functions in MySQL enable advanced data analysis by performing calculations across rows without collapsing the result set. The COUNT() window function specifically allows counting elements within a defined window partition while preserving individual row details. How Window Functions Work Unlike traditional aggregate functions that group ...

Database Schema Setup Create tables for identity cards and students, where each student references one card via a foreign key. CREATE TABLE identity_cards ( card_id INT PRIMARY KEY, card_number VARCHAR(20) ); CREATE TABLE students ( student_id INT PRIMARY KEY, student_name VARCHAR(10), card_ref INT, FOREIGN KEY (card_re ...

Creating a Practice Database and Tables The standard MySQL database for common operations is db_school, while db_practice serves as a learning environment. Understanding how to create tables, modify their structure, and define constraints is fundamental for effective database management. Setting Up the Practice Environment # Remove existing ...

Database Table Setup First, create a sample MySQL table for demonstration: DROP TABLE IF EXISTS products; CREATE TABLE products ( id INT PRIMARY KEY AUTO_INCREMENT, product_name VARCHAR(50), vendor_name VARCHAR(50), price INT, details VARCHAR(200), available INT ); INSERT INTO products (product_name, vendor_name, price ...

Paginatoin with Separate Count Query When implementing pagination in SQL Server, one common approach is to execute two separate queries—one to retrieve the total record count and another to fetch the actual data page. -- Retrieve total number of matching records SELECT COUNT(*) AS TotalRecords FROM Products WHERE CategoryId = 5 AND IsActive = 1 ...

Data Definition Language (DDL) Database Operations Creating Databases -- Create a new database CREATE DATABASE db_name; -- Create database only if it doesn't exist CREATE DATABASE IF NOT EXISTS db_name; -- Create database with specific character set CREATE DATABASE db_name CHARACTER SET charset_name; -- Example: Create db4 with gbk charset ...