Oracle SQL Basics

Oracle is a relational database. Relational databases store data in tables like this:

COUNTRY

CTRY_ID	CTRY_NAME	CTRY_AREA	CTRY_POP	POP_UPD_AT	CURRENCY
14	Germany	137882	82046000	30-nov-08	Euro
48	Ghana	92100	23837000	null	Cedi
53	Australia	2969907	21884000	4-sep-09	Australian Dollar
73	Greece	50949	11257285	1-Jan-09	Euro
122	Georgia	26900	4382100	1-Jan-09	Lari
123	New Zealand	104428	4320300	4-sep-09	New Zealand Dollar
147	Gambia	4361	1705000	null	Dalasi
149	Gabon	103347	1475000	null	CFA franc

Communication with the database is performed using Structured Query Language (SQL).

SQL is used to create, alter and destroy tables in the database and to insert, update, delete and query the data in these tables.

Applications may use APIs and frameworks such as ODBC, JDBC, JPA and Hibernate, but ultimately these will all talk to the database using SQL.

SQL consists of:

The SELECT statement
Data Manipulation Language (DML)
Data Definition Language (DDL)

Let's take a tour of SQL, starting with the SELECT statement.

select