> For the complete documentation index, see [llms.txt](https://help.holixa.com/holixa-erp-connector/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.holixa.com/holixa-erp-connector/data-interface-reference-manual/data-tables-relations.md).

# Data tables, relations

all tables have their system(aka base or fixed) fields described in this chapter;

marked tables (EcENTITY & EcASSOC) are expected to be extended by additional (custom) fields; these fields can be created by a consultant using for e.g. MS SQL Management Studio

![](/files/eysYMB6IUQA5BU7cddZY)