A set of data that gives information about other data. Examples of relational-database metadata include:
– Tables of all tables in a database, their names, sizes, and number of rows in each table. – Tables of columns in each database, what tables they are used in, and the type of data stored in each = column. In database terminology, this set of metadata is referred to as the catalog. The SQL standard specifies a uniform means to access the catalog, called the information schema, but not all databases implement it, even if they implement other aspects of the SQL standard.