A data structure used for fast access to rows in a table. An index is usually built for the primary key of each table and can then be used to quickly find a particular row. Indexes are also defined and built for other attributes when those attributes are frequently used in queries.
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Primary key
One or more attributes that contain values that uniquely identify each row. For example, a customer table might have the primary key of cust ID. The cust ID attribute is then assigned a unique value for each customer. A primary key is a constraint of most tables.
Constraints
Restrictions or limitations on tables and attributes. For example, a wine can be produced only by one winery, an order for wine can’t exist if it isn’t associated with a customer, having a name attribute could be mandatory for a customer.
SQL
A query language that interacts with a DBMS. SQL is a set of statements to manage databases, tables, and data.
Relational database management system
A software system that manages data in a database and is based on the relational model. DBMSs have several components
Relational model
A model that uses tables to store data and manage the relationship between tables.
Rows
The data entries in a table. Rows contain values for each attribute. For example, a row in a customer table might contain the values “Matthew Richardson,” “Punt Road,” and “Richmond.” Rows are also known as records.