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

![](https://2469526073-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FdP4aGs76nJ1Aw5NABOmE%2Fuploads%2F2b3FWUHSPPPrfmD5SivB%2Fimage.png?alt=media\&token=12eac5a3-c00b-498d-a648-d871bb5e8b3a)