This post shows you how to write SQL command to add unique constraint into a table and how to make unique constraint right at the time we create the table.
A unique constraint is a single field or combination of fields that uniquely defines a …
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This example will show you SQL to add foreign key constraint in to a table. This SQL tested with Oracle database but you can apply into any other relational database such as: MariaDB, MySQL, MSSQLSERVER.
The SQL command looks like this:
ALTER TABLE TABLEA
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To kill sessions from a user, we first find all sessions belongs to this user. We can do it with table V$SESSION.
To select all sessions belong to an user:
SELECT SID, SERIAL# FROM V$SESSION WHERE USERNAME = 'ABC';
Then, with SID and SERIAL#, we …
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I will show you how to read/find remembered passwords saved in Toad. It’s a little tricky but a very handful tips for your DBA job.
First of all your new session window looks like this:
New session window in Oracle Toad software
Toad is a …
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This SQL will help you list all current active processes in Oracle as a DBA. You will need SYS account or an account with granted privilege to run this command.
Just copy and paste to run on SQL Developer or Toad with SYS account logged …
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This post will show you what is PK, FK in rational databases such as Oracle, MySQL, Postgre, MSSQLServer. They are basics but they are also important.
What is PK – Primary Key
PK or Primary Key is the unique, not null column in the table. …
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This post show you how to start/stop/restart and check status of MySQL/MariaDB database on Ubuntu.
Start MySQL/MariaDB database
This command used to startup MySQL database on Ubuntu:
# systemctl start mysql.service
Your output will look like this
mysql.service - MySQL Community Server
Loaded: loaded (/lib/systemd/system/mysql.service;
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Tuning and optimizing MySQL/MariaDB to run on a weak box with 512MB RAM for 1-5 WordPress websites running on is a big challenge. Since the cloud providers need you to pay more money on their products, they rarely have tutorial like this.
Set MariaDB/MySQL max
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This post will guide you how to find/list all duplicated records in a table in the fastest way. This command also not make your database slower since its a lightweight SQL.
SELECT * FROM TBLA WHERE ID IN (
SELECT ID FROM (SELECT
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In this tutorial, we’ll use “
INSERT INTO SELECT FROM” structure to build an SQL to insert data from a select query to an existing table in MS SQLSERVER (tested with version 2008) General syntax of “INSERT INTO SELECT FROM”
INSERT INTO TableA SELECT …
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