PL/SQL is an Oracle-specific language. PL/SQL is Oracle's procedural extension to SQL. With PL/SQL, you can use variables, perform actions in loops, call subroutines and perform conditional (IF-THEN-ELSE) branching.
In order to be a top-notch Oracle professional, one needs to know SQL and PL/SQL pretty well. Learning SQL and PL/SQL does not mean an automatic transition to data warehousing. You must know SQL and PL/SQL to interact with the Oracle database whether it is being used as a data warehouse or an OLTP system. So if you are interested in data warehousing, learn SQL and PL/SQL.
Teradata is a company that competes with Oracle Corporation. Teradata's database system is specifically designed to hold large quantities of data. Teradata systems do not work well for OLTP systems, those with short, quick transactions. Oracle's database system is designed to meet all needs. There are many Teradata data warehouses in use today. And there are many Oracle data warehouses out there too.
I'm not sure what the market for Teradata is. I only have a passing interest in Teradata so I do not keep up on it nearly as much as I do with Oracle.
This was first published in August 2006