Listing all tables and their table counts in a MySQL database
The Following SQL query will list all tables in a MySQL database and also list the row counts for each. where mydatabase is the name or your database. The output…
Database normalization and normal forms
The goal of database normalization is to reduce data redundancy and to improve data integrity. This is done by organizing columns and tables by apply the normal forms. In theoretical…
Quick Introduction to Hive
Hive is an SQL language that processes and analyzes data in Hadoop. It does not require knowledge of any programming language. Hive is not suitable for OLTP, it is designed…
Copying a large database from one server to another
Recently, I had to copy a large database from one server to another. I had 100G free on the source server. Unfortunately, the server would run out of memory before…
ORA-01858: a non-numeric character was found where a numeric was expected
Error Message What it means This error occurs if a wrong value is passed when converting a number or string to date. Solution To fix this problem, find out what…
Finding duplicate values in a MySQL database
In the following query, we list all lastname held by 2 or more employees. If you want a value to be unique, you should add a unique constraint to the…
How to reset MySQL root password
To reset MySQL password, you need to have root access to the machine. After logging in as root, start by shutting down MySQL: Verify that all mysql processes have been…
How can I change the filesize limit for imported files in PhpMyAdmin
The filesize limit is not defined in PhpMyAdmin. The limit is taken from php.ini file. To change this limit, you needed to edit your php.ini file: Change the following two…
Oracle decode() function
Decode function has the same functionality as an IF-THEN-ELSE statement. It is present in Oracle 9i and above. It has the syntax For example, This is like saying the following…
What is an Oracle Package
A package is an encapsulated collection of related PL/SQL types, objects, procedures, and other program objects. Packages have a package specification and a package body. Package specification declares constants, variables,…