HIVE-28084: Iceberg: COW fix for Merge operation

[deniskuzZ]

What changes were proposed in this pull request?

Fix the subquery union sql

Why are the changes needed?

BugFix

Does this PR introduce any user-facing change?

No

Is the change a dependency upgrade?

No

How was this patch tested?

mvn test -Dtest=TestIcebergLlapLocalCliDriver -Dqfile=merge_iceberg_cow.q -Drat.skip=true -Dtest.output.overwrite=true

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarCloud