1. A method comprising: determining relationship types between at least some data items of a plurality of data items extracted from a plurality of data sources and integrated into a plurality of tables in a database, wherein the relationship types are based on respective data sources from which the data items have been extracted, the relationship types including at least two of the following: a first relationship type, a second relationship type, a third relationship type, and a fourth relationship type, wherein: the first relationship type is between first and second data items extracted from a first structured data source, the second relationship type is between data items extracted from different structured data sources, wherein the second relationship type is based on a plurality of respective first relationship types, the third relationship type is between a data item extracted from a second structured data source, and an entity table including, as entity table data items, attributes about a first unstructured data source, and wherein the data item extracted from the second structured data source is mentioned in the first unstructured data source, and the fourth relationship type is between two data items that: have been integrated from different structured data sources, and are both mentioned in a second unstructured data source; and displaying, on a user interface, relationship type indicia to indicate relationship types between displayed data items, the relationship type indicia including at least one of first indicia to indicate the first relationship type, second indicia to indicate the second relationship type, third indicia to indicate the third relationship type, and fourth indicia to indicate the fourth relationship type.