Assure CA Datacom SQL PTFs 15.1 SO01886 (SO04015) and SO04034 which provide the enhancement are applied.
For documentation on this enhanced feature, refer to CA Datacom Core - 15.1 section "Using Nested Table Expressions (NTE)" https://docops.ca.com/ca-datacom/15-1/en/using/using-sql/using-nested-table-expressions-nte