Structured Query Language (SQL) is a standard language that is widely used for accessing and manipulating the data stored in a relational database. SQL has evolved over the years into a highly complex language that can do a vast variety of things to your database. SimpleDB does not support the complete SQL language, but instead it lets you perform your data retrieval using a much smaller and simpler subset of an SQL-like query language. This simplifies the whole process of querying your data. A big difference between the simpler SQL supported by SimpleDB and SQL is the support for multi-valued SimpleDB attributes, which makes it super simple to query your data and get back multiple values for an attribute.
The syntax of the SimpleDB SQL is summarized in this syntax:
select output_list from domain_name [where expression] [sort_instructions] [limit limit]
We will go into detail on SimpleDB SQL in Chapter 6,Querying.