1 files changed, 18 insertions, 0 deletions
diff --git a/sqlglot/optimizer/merge_subqueries.py b/sqlglot/optimizer/merge_subqueries.py
index 3e435f5..3c51c18 100644
--- a/sqlglot/optimizer/merge_subqueries.py
+++ b/sqlglot/optimizer/merge_subqueries.py
@@ -119,6 +119,23 @@ def _mergeable(outer_scope, inner_select, leave_tables_isolated, from_or_join):
     Returns:
         bool: True if can be merged
     """
+
+    def _is_a_window_expression_in_unmergable_operation():
+        window_expressions = inner_select.find_all(exp.Window)
+        window_alias_names = {window.parent.alias_or_name for window in window_expressions}
+        inner_select_name = inner_select.parent.alias_or_name
+        unmergable_window_columns = [
+            column
+            for column in outer_scope.columns
+            if column.find_ancestor(exp.Where, exp.Group, exp.Order, exp.Join, exp.Having, exp.AggFunc)
+        ]
+        window_expressions_in_unmergable = [
+            column
+            for column in unmergable_window_columns
+            if column.table == inner_select_name and column.name in window_alias_names
+        ]
+        return any(window_expressions_in_unmergable)
+
     return (
         isinstance(outer_scope.expression, exp.Select)
         and isinstance(inner_select, exp.Select)
@@ -137,6 +154,7 @@ def _mergeable(outer_scope, inner_select, leave_tables_isolated, from_or_join):
             and inner_select.args.get("where")
             and any(j.side in {"FULL", "RIGHT"} for j in outer_scope.expression.args.get("joins", []))
         )
+        and not _is_a_window_expression_in_unmergable_operation()
     )