Database Reference
In-Depth Information
A surrogate key is the most effective and efficient method of both apply-
ing Referential Integrity and accessing single-row data items in OLTP-type,
high-concurrency transactional databases. Obviously, complex composite
primary key values are suited for data warehouse and reporting tables.
Why? Multiple-column indexes are presorted. The exception is where
reporting tables are accessed in more than a single sorted order. Of course,
specialized goodies such as clusters, index-organized tables, and material-
ized views can be utilized.
Next we will look at the origins of SQL and what Oracle SQL is.
1.3
Structured Query Language (SQL)
1.3.1
The Humble Origins of SQL
Why are we going backward in time looking at things no longer in use? In
order to understand SQL code effectively, we need to understand the most
basic forms of SQL, having much to do with why SQL was invented in the
first place. In short, SQL database access has evolved with data modeling
techniques, Oracle Database, and other databases. SQL is pronounced
“sequel” or “ess-queue-ell.” The acronym SQL represents the term Struc-
tured Query Language.
SQL is a language used to query a structured (Relational) data set in a
logically consistent manner.
Note:
The query language used to access an Object database is called ODQL.
ODQL stands for Object Definitional Query Language. The acronym “QL”
thus means “query language,” a language used to query a database.
SQL in its most primitive form stems from the idea of a reporting lan-
guage devised in theory by the inventor of the Relational data model. The
roots of SQL lie in retrieval of data sets. What this means is that SQL is
intended as a language to retrieve many rows from one or many tables at
once, a result set. SQL was not originally intended to retrieve individual
rows from a relational database as exact row matches in transactional or
OLTP databases. However, SQL can now be used to do precisely that, and
fairly efficiently.
What does all of this mean without using another plethora of nasty long
words? SQL was developed as a shorthand method of retrieving informa-
tion from relational databases and has become the industry standard over
