An embedded join is an equijoin that you define in a Master File. The name comes from the fact that the join definition is "embedded" in the Master File. (This is also known as a cluster join.)
You can define an embedded join between data sources:
In the following heterogeneous embedded join, A = a DB2 table, B = a CA-IDMS/DB record, and C = an IMS segment.
In a Master File, each segment declaration describes one RDBMS table or view, or one record. You can include up to 64 segments in an embedded join.
The entire join structure described by the Master File is referred to as a tree.
A subtree is a segment and any directly related descendant segments of the same data source type. A root subtree is the subtree at the top of the tree.
There are four subtrees here:
Note that B¹-B¹ and B² are separate subtrees because, even though they are of the same data source type, they are not directly related.
The root subtree is A-A-A.
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