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Relationships

Real data is connected: orders belong to customers, jobs to sites, tasks to projects. appTown connects tables with link fields.

#Link two tables

Give one table a Link to another table field. For example, Orders gets a Customer field that links to Customers.

• Turn on Allow several to link to more than one record (an order with several products).
• The other table shows the link back automatically, under Linked from, on each record's detail view: a customer lists their orders.
• Build → Data lists every relationship in the app.

#Use linked data

• In views, a link shows the linked record's display field, and opens it on tap.
• In expressions, follow a link with a dot: [Customer].[Email], [Order].[Customer].[Name].
• Totals across a link: sum or count the records that point at this one with SELECT and [_THISROW]:

SUM(SELECT(Orders[Total], [Customer] = [_THISROW]))
COUNT(FILTER("Orders", AND([Customer] = [_THISROW], [Status] = "Open")))

Formulas like these are calculated again when a linked record changes. See FILTER and SELECT.

#Kanban by a link

A kanban view can use a link field for its columns: jobs in one column per technician's team, for example.

#Removing linked tables

A table can't be removed while other tables link to it. Change or remove those link fields first. Removing never deletes data: see Tables and fields.