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A mapping that joins two sources

What this example shows

How a single target entity is filled from more than one source - the join, the condition that drives it, and how the two sources are kept in order.

It is the end state of Creating a Mapping with Multiple Sources.

Branch: examples → mapping → with-multiple-sources

What changed

Everything from the mapping with an expression, plus a Product entity and a Product mapping that combines two source objects:

sources:
  - id: ProductSource
    entity: JuiceERP.Product
    join: from
  - id: PhysicalProductSource
    entity: JuiceERP.PhysicalProduct
    join: left-join
    dependencies:
      - ProductSource
    conditions:
      - ProductSource.ProductID = PhysicalProductSource.ProductID

How multiple sources fit together

join gives each source a role. Exactly one source is the from; the rest join onto it. Here PhysicalProductSource is a left-join, so products without a physical counterpart still appear in the result - a deliberate choice, since JuiceERP also has digital products.

dependencies declares what a source needs before it can be joined. PhysicalProductSource depends on ProductSource, which is what lets CrossModel order the joins correctly. In a mapping with three or more sources, this is what stops the generated SQL referencing a table before it has been introduced.

conditions is the join predicate, written in terms of source object ids rather than table names - the same {{…}}-free reference style used throughout mappings.

Relationships can supply the condition for you

From v1.4.0 a dependency can point at a relationship instead of a hand-written condition. CrossModel then derives the join conditions from that relationship and shows them as read-only rows. If the two source objects are already related in the model, prefer that - the condition stays correct when the relationship changes. This example uses an explicit condition, which is what you need when no relationship exists between the two sources.

What to look at

  • The mapping diagram. Two source objects on the left feeding one target. This is the shape worth recognising: integration logic is visible as structure, not buried in SQL.
  • The Dependencies grid. Open PhysicalProductSource from the mapping's Sources grid to see its Source and Relationship columns, and the condition below.

Where to go next