Finding Duplicate Values in MySQL: A Guide

 Finding Duplicate Values in MySQL: A Guide

Setting up a sample table

CREATE TABLE callme (
    id INT PRIMARY KEY AUTO_INCREMENT,

    first_name VARCHAR(50) NOT NULL,
    last_name VARCHAR(50) NOT NULL,
    email VARCHAR(255) NOT NULL
);

Second, inserts rows into the callme table

INSERT INTO callme(first_name,last_name,email)

VALUES ('Carine ','Schmitt','carine.schmitt@verizon.net'),
       ('Jean','King','jean.king@me.com'),
       ('Peter','Ferguson','peter.ferguson@google.com'),
       ('Janine ','Labrune','janine.labrune@aol.com'),
       ('Jonas ','Bergulfsen','jonas.bergulfsen@mac.com'),
       ('Janine ','Labrune','janine.labrune@aol.com'),
       ('Susan','Nelson','susan.nelson@comcast.net'),
       ('Zbyszek ','Piestrzeniewicz','zbyszek.piestrzeniewicz@att.net'),
       ('Roland','Keitel','roland.keitel@yahoo.com'),
       ('Julie','Murphy','julie.murphy@yahoo.com'),
       ('Kwai','Lee','kwai.lee@google.com'),
       ('Jean','King','jean.king@me.com'),
       ('Susan','Nelson','susan.nelson@comcast.net'),
       ('Roland','Keitel','roland.keitel@yahoo.com');

 

 

 Now query  this

SELECT * FROM callme
ORDER BY email; 

For example, to find rows in the callme table with duplicate values in first_name, last_name, and email column, you use the following query:

 

mysqltutorial .org  source
 

list of 5 tools that Oracle developers need:

1. Oracle SQL Developer: A free, integrated development environment (IDE) for developing, debugging, and running SQL applications.
2. Oracle Data Modeler: A desktop application for designing and managing database models.
3. Oracle Application Express (APEX): A low-code platform for developing and deploying web applications on Oracle Database.
4. Oracle PL/SQL Developer: A commercial IDE for developing, debugging, and running PL/SQL applications.
5. Oracle JDeveloper: A commercial IDE for developing and deploying Java applications on Oracle Database.

Oracle developers need a variety of skills, including:

• SQL: SQL is the programming language used to communicate with Oracle databases. Oracle developers need to be proficient in SQL in order to write queries, create and update database objects, and manage data.
• PL/SQL: PL/SQL is a procedural language that can be used to extend the functionality of SQL. Oracle developers need to be proficient in PL/SQL in order to write stored procedures, functions, and triggers.
• Oracle database architecture: Oracle developers need to understand the architecture of Oracle databases in order to design, develop, and deploy efficient and scalable applications.
• Oracle database administration: Oracle developers need to have some knowledge of Oracle database administration tasks, such as creating and managing databases, backing up and restoring databases, and tuning database performance.
• Software development skills: Oracle developers need to have general software development skills, such as programming, testing, and debugging

Some popular IDEs for Oracle developers include:

• Oracle SQL Developer
• Oracle Data Modeler
• Oracle Application Express (APEX)
• Oracle PL/SQL Developer
• Oracle JDeveloper
• Oracle Toad for Oracle
• PL/Vision

tips and bottlenecks for Oracle Application Express (APEX):

Tips:

• Use the APEX built-in wizards and templates to quickly get started with developing applications.
• Use the APEX Page Designer to create and edit pages visually, without writing any code.
• Use the APEX Region Plug-ins to add pre-built functionality to your pages, such as grids, charts, and forms.
• Use the APEX Theme Roller to customize the look and feel of your applications.
• Use APEX Security to protect your applications from unauthorized access.
• Use APEX Performance Monitor to identify and resolve performance bottlenecks.

Bottlenecks:

• Database queries: APEX applications rely heavily on database queries, so it is important to optimize your queries for performance.
• Page rendering: APEX pages can be complex, which can lead to rendering performance bottlenecks.
• Session management: APEX applications manage sessions for each user, which can lead to performance bottlenecks if there are a large number of concurrent users.
• Network bandwidth: APEX applications can generate a lot of network traffic, which can lead to performance bottlenecks if the network bandwidth is limited.

Here are some tips for avoiding performance bottlenecks in APEX applications:

• Use a database performance monitoring tool to identify slow queries.
• Use APEX SQL Tuning Advisor to get recommendations for improving the performance of slow queries.
• Use APEX caching to reduce the number of database queries that are executed.
• Use APEX minification and compression to reduce the size of page resources.
• Use APEX session pooling to reduce the number of database sessions that are created.
• Use a load balancer to distribute traffic across multiple servers.
• Upgrade your network infrastructure to increase bandwidth.