"SQL stands for Structured Query Language, which is pronounced either as S Q L (as the three letters) or as Sequel. It appears that the former pronunciation is more common in the UK and the latter in the US -- but as the two are interchangeable, it shouldn't be a cause of anxiety.
The DDL section is used for creating database objects, such as tables. In practice, people often use a GUI for creating tables and so on, so it is less common to hand-write DDL statements than it used to be. However an example looks like this:
CREATE TABLE Foo
(MajorPartNum LONG NOT NULL, MinorPartNum LONG NOT NULL,
Quantity LONG NOT NULL,
CONSTRAINT MajorMinor PRIMARY KEY
(MajorPartNum, MinorPartNum) );
The DML section is used to manipulate the data such as querying it. While is also common to use a query builder to create queries, people do still hand-craft DML statements, such as queries. An example might look like this:
SELECT Item, Amount, SaleNo
WHERE Item = 'Sofa'
ORDER BY SaleNo;
- Do you have questions about data definition language (DDL) and data manipulation language (DML)? Ask our expert!
This was first published in April 2008