Database - Wy Lee

Wy Lee

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Database

This tag is about the Database.

Database : Optimistic and Pessimistic Locks

Recently, I had a conversation with a senior software engineer about this topic, and I found it very fruitful, so I organized the topic we discussed a bit as a record. Optimistic and Pessimistic Locks In a system with spike in traffic, these two locks are dealing with different issues

SQL basics : use of group by and having

The purpose of this article is to record my understanding of the basic usage of GROUP BY and HAVING in SQL. Group by * Used with aggregate function * If there are multiple different numbers in a field that need to be calculated, they can be seen as a group * Use where

Database Normalization

The primary objective of database normalization is to minimize the duplication of data within a table by * seperating the unrelated data into individual tables * encouraging the use of relationships to connect different tables Pros 1. Reduces Data Redundancy: By breaking down data into smaller related tables, it helps to conserve

Some learning on ACID, Transaction in DBMS(Database Management System)

The first time I heard about concept of the transaction in SQL is back to the days when I was at my previous job to handle, manage and check API calling error to see if the data was successfully written into the Database ,which there is rollback or commit on

Intro of JPA, Hibernate, and ORM

I am writing this article to recap my learning on JPA and Hibernate,as recently I am building my project with this framework. And Hibernate, also a framework to speed up and simplify the process of database connection, is a solution to ORM. Traditionally we use JDBC to implement SQL

Intro of SQL injection

This article is a recap of SQL Injection, including the purpose of this attack method and attack examples, as well as ways to prevent SQL Injection. In addition, at this stage I focus on the combination of Java and SQL, so I will mention it a bit. Introduction of SQL

SQL join : impact on Performance

This article is to record my learning on different join syntax on SQL and the performance how we select these. The join syntax can obtain data from multiple tables, and when it comes to inner join , left join and right join to obtain data from to relational tables, use inner