How to empty a MySQL database
Emptying a databases involves dropping (deleting) all its tables. If you have a hundred tables in your database, the task becomes cumbersome. The easiest way to do this is to…
MySQL column enumeration example
Problem: You are building a database and you have a field that can accept only certain responses. For example, there is a Gender column which accepts only M or F…
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…
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,…
Commonly used code in Oracle
Changing case To change the first letter of the word to cap, use the inicap function. Use upper to covert to uppercase and lower to convert to lower case. Examples:…
What is PL/SQL
Procedural Language extension of SQL (PL/SQL) combines SQL with procedural programming features such as looping, conditionals, and reusable blocks. PL/SQL engine processes PL/SQL statements. PL/SQL statements can reside on the…
Oracle set operators: union, intersect, minus
The most commonly used set operators in Oracle are: union intersect minus Union Union combine results returned by two or queries into a single table. In a union, all tables…