/ doc / toc / ARCQuery / Class / QueryExpressionRel / __TOCDet / Description

Description

Edit keys at this level only

= Enables 'jumping' or 'travelling' from a collection of one entity type to another (related) entity type.0x000D0x000A0x000D0x000AEnables queries like0x000D0x000A'Order/WHERE Amount 0x003E 10000 EUR/REL Customer/REL SupportTicket'0x000D0x000Awhich will show support tickets for all customer who at some time have ordered something for at least 10 000 EUR.0x000D0x000A0x000D0x000ACorresponds (very) coarsely to the JOIN concept in SQL0x000D0x000A0x000D0x000AThere are two ways for this to happen:0x000D0x000A0x000D0x000A1) -ToMany-:0x000D0x000AIf -IPRelationsKeysPointingTo- has a link for the current entity type, like 'Customer' having a link to 'Order' then a jump from a collection of Customers can be made to for instance an Order collection by iterating through all Orders with CustomerId present in the collection of Customers.0x000D0x000A0x000D0x000A2) -ToOne-:0x000D0x000AA jump from a collection of 'OrderLine' to 'Order', or 'Order' to 'Customer' can be made by iterating through the whole collection looking for respectively 'OrderId = xxx' and 'CustomerId = xxx' properties.0x000D0x000A0x000D0x000AVariant 1) (-ToMany-) will be the default attempted. Note how this depends on a more strongly typed schema (existence of entity classes, and -PK-s).0x000D0x000AIf 1) is not found, then variant 2) (-ToOne-) will be attempted.0x000D0x000A0x000D0x000ANOTE: The relevant keys for 'jumping' must exist. If you for instance do like this (admittedly meaningless query, but it explains the point though):0x000D0x000ANOTE:   'Order/WHERE Amount 0x003E 10000 EUR/SELECT Amount, Created/REL Customer'0x000D0x000ANOTE: then the key CustomerId is not available, and the jumping breaks down.0x000D0x000ANOTE:   'Order/WHERE Amount 0x003E 10000 EUR/SELECT CustomerId, Amount, Created/REL Customer'0x000D0x000ANOTE: on the other hand would work (but use of SELECT is meaningless anyway of course).0x000D0x000A0x000D0x000ASee -SyntaxHelp-.

Edit keys at all sub levels.
NOTE: Edits are always additive. Use 'Invalid' in order to delete keys.

Generated 2025-12-13 03:46:15.183 UTC