Basic SQL Queries

Database and query basics

Databases are computer applications which can store data in an organized way. The most common structure for data stored within a database is a table, which contains records. Each record within the table corresponds to one thing, such as a person, or a sales receipt. Records contain fields, each of which holds data of one particular type, such as the total amount for a receipt, or a person's age. Records correspond to rows in the table, while fields correspond to columns. Within each record, there is some type of unique identifying information, such as a numeric ID.

When using a database management system to access the data within a database, records are extracted by performing queries. These queries can contain parameters that refer to values stored within particular fields, to return a specific subset of the data. Simple queries are performed on one specific table, but more complex queries can join multiple tables together.

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