What Is SQL?
SQL, which stands for Structured Query Language, is a language designed to extract, organize, and update information in relational databases. Originally, SQL was envisioned as an English-like query language that untrained end users could use to access and update relational database data. But in reality, SQL is nothing like English, and it's far too complicated and esoteric for untrained users. But it has become the overwhelming favorite among programmers who develop applications that access relational databases.
Like most computer languages, SQL has several different dialects. In fact, each major brand of SQL database server has its own dialect of SQL. These dialects are 95 percent the same, so a basic SQL statement is likely to work the same regardless of the database server you use it with. But there are many variations in how the more advanced features of SQL work.
The version of SQL used by Microsoft's SQL Server is known as T-SQL.
Like other programming languages, SQL uses statements to get its work done. Table-1 lists the most commonly used statements.Table-1 Common SQL Statements
SQL Statement What It Does use Identifies the name of the database that subsequent SQL statements apply to. select Retrieves data from one or more tables. This is the SQL statement that's used the most. insert Inserts one or more rows into a table. delete Deletes one or more rows from a table. update Updates existing rows in a table. create Creates tables and other database objects. alter Alters the definition of a table or other database object. drop Deletes a table or other database object.
Here's something you've probably wondered ever since you first saw the letters SQL: How do you pronounce it? Two schools of thought exist on the subject:
- Spell out the letters: S-Q-L.
- Pronounce it like the word sequel.
Either way is acceptable, but sequel is hipper. You can always tell how a writer pronounces SQL by checking to see if the author writes "a SQL query" or "an SQL query."
You can impress even the staunchest SQL expert by pointing out that originally, the language was spelled SEQUEL by the IBM engineers who created the first version way back in the 1970s. SEQUEL stood for Structured English Query Language. Someone must have correctly pointed out that aside from borrowing a few words from English such as select and CREATE, SEQUEL actually bore no resemblance whatsoever to English. So English was dropped from the name and the acronym was shortened from SEQUEL to just SQL.