# Getting started with Oracle Database
# Hello World
SELECT 'Hello world!' FROM dual;
In Oracle's flavor of SQL, "dual is just a convienence table" (opens new window). It was originally intended (opens new window) to double rows via a JOIN, but now contains one row with a
DUMMY value of 'X'.
# SQL Query
List employees earning more than $50000 born this century. List their name, date of birth and salary, sorted alphabetically by name.
SELECT employee_name, date_of_birth, salary FROM employees WHERE salary > 50000 AND date_of_birth >= DATE '2000-01-01' ORDER BY employee_name;
Show the number of employees in each department with at least 5 employees. List the largest departments first.
SELECT department_id, COUNT(*) FROM employees GROUP BY department_id HAVING COUNT(*) >= 5 ORDER BY COUNT(*) DESC;
# Hello world! from table
# Create a simple table
create table MY_table ( what varchar2(10), who varchar2(10), mark varchar2(10) );
# Insert values (you can omit target columns if you provide values for all columns)
insert into my_table (what, who, mark) values ('Hello', 'world', '!' ); insert into my_table values ('Bye bye', 'ponies', '?' ); insert into my_table (what) values('Hey');
# Remember to commit, because Oracle uses transactions
# Select your data:
select what, who, mark from my_table where what='Hello';
# Hello World from PL/SQL
/* PL/SQL is a core Oracle Database technology, allowing you to build clean, secure, optimized APIs to SQL and business logic. */ set serveroutput on BEGIN DBMS_OUTPUT.PUT_LINE ('Hello World!'); END;
Oracle (opens new window) is a relational database management system (RDBMS) originally built by Larry Ellison, Bob Miner, and Ed Oates in the late 70s. It was intended to be compatible with IBM's System R (opens new window).