An identifier is a string used to reference a database, table, or field. Identifiers follow the standard SQL rules. Since a UnityJDBC query may span multiple databases, table and field identifiers defined in a data source may not be unique across all data sources. In which case, the database name should be added to the identifier to create a unique system-wide identifier. For instance, consider an order database given the name OrderDB with a table called Orders and fields id and orderDate. The Orders table may be referred to using only Orders or OrderDB.Orders. Similarly, the field id may be referred to as Orders.id or OrderDB.Orders.id. Standard aliasing using AS in the FROM and SELECT clauses is supported. Delimited identifiers are supported by enclosing in double quotes (e.g. "from" or "my field with spaces"). Delimited identifiers must be used for SQL reserved words.