"group"
This type gives a possibility to link records of one table to other records of the same table, but not by "parent" principle as in the "parent" data type. It works by storing ids of records glued with comma in regular table cell. A fine sample of use is the accompanying products in online store when you need to link one product with several others and then as quickly as possible find them and display near the initial product. It's a specific analogy like "Many to many" within one table.
Field type in SQL table: if one record is related to some others, "varchar" type is enough, if there are many records, then "text" type might be needed. The cell of the table will be getting ids of the linked records separated by a comma, for example "2,63,82".
Additional parameters
"name_field"
Purpose: if there is no "name" field in the linked model, you need to specify a nominal field
Possible values: text, for example "title"
By default: not set
"long_list"
Purpose: applicable if the list of values has long length, then the values will be received with the help of search string without "select" tag
Possible values: "true", "false"
By default: "false"
Samples of use are located in the Group section.
Previous section
"many_to_many"