FIX: Update rowcount in nextset()

CHANGELOG.md

@@ -104,6 +104,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
   before; users should call `cursor.setinputsizes()` to work around this.
 
 ### Fixed
+- **GH-863:** `Cursor.nextset()` now refreshes `Cursor.rowcount` for
+  the result it moves to, as `execute()` does: the affected-row count for an
+  INSERT/UPDATE/DELETE/MERGE result and -1 for a result set. Previously
+  `rowcount` kept the value of the first statement of a multi-statement batch,
+  so the rows affected by later statements (for example each INSERT of a
+  T-SQL `WHILE` loop) could not be read. This matches pyodbc.
 - **GH-855:** Bulk copy and internal async queries load the Rust extension directly
   when upgrading from 1.15.0 removes `mssql_py_core/__init__.py`. Existing affected
   installations can restore the initializer with

mssql_python/cursor.py

@@ -3288,6 +3288,15 @@ def nextset(self) -> Optional[bool]:
             # If describe fails, there might be no results in this result set
             self.description = None
 
+        # Update rowcount for the new result, as execute() does: -1 for a
+        # result set, the affected-row count for INSERT/UPDATE/DELETE/MERGE.
+        # Without this, rowcount keeps the value of the first statement of a
+        # multi-statement batch (pyodbc refreshes it here too).
+        if self.description:
+            self.rowcount = -1
+        else:
+            self.rowcount = ddbc_bindings.DDBCSQLRowCount(self.hstmt)
+
         logger.debug(
             "nextset: Moved to next result set - column_count=%d",
             len(self.description) if self.description else 0,

tests/test_004_cursor.py

@@ -7691,6 +7691,78 @@ def test_cursor_messages_nextset_trailing_print(cursor):
     assert not cursor.nextset()
 
 
+def test_nextset_updates_rowcount(cursor, db_connection):
+    """Test that nextset() refreshes rowcount for each statement of a batch.
+
+    execute() sets rowcount from the first statement only; each later
+    INSERT/UPDATE/DELETE result must report its own count after nextset(),
+    and a result set must report -1, as after execute().
+    """
+    try:
+        cursor.execute("CREATE TABLE #nextset_rowcount (id INT)")
+        db_connection.commit()
+
+        cursor.execute("""
+            INSERT INTO #nextset_rowcount VALUES (1);
+            INSERT INTO #nextset_rowcount VALUES (2), (3);
+            SELECT id FROM #nextset_rowcount;
+            UPDATE #nextset_rowcount SET id = id + 10;
+            DELETE FROM #nextset_rowcount WHERE id = 99;
+            """)
+        assert cursor.rowcount == 1, "execute() should report the first INSERT"
+
+        assert cursor.nextset()
+        assert cursor.rowcount == 2, "nextset() should report the second INSERT"
+
+        assert cursor.nextset()
+        assert cursor.description is not None
+        assert cursor.rowcount == -1, "A result set should report -1 before fetching"
+        assert len(cursor.fetchall()) == 3
+
+        assert cursor.nextset()
+        assert cursor.rowcount == 3, "nextset() should report the UPDATE"
+
+        assert cursor.nextset()
+        assert cursor.rowcount == 0, "nextset() should report a DELETE matching no rows"
+
+        assert not cursor.nextset()
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #nextset_rowcount")
+        db_connection.commit()
+
+
+def test_nextset_rowcount_in_loop_batch(cursor, db_connection):
+    """Test that the per-statement counts of a T-SQL loop can be summed.
+
+    A WHILE loop sends one result per INSERT; summing rowcount over
+    nextset() must give the number of rows the batch inserted. Each
+    iteration inserts a different number of rows (1, 2, 3), so a stale
+    rowcount cannot add up to the right total by accident.
+    """
+    try:
+        cursor.execute("CREATE TABLE #nextset_loop (id INT)")
+        db_connection.commit()
+
+        cursor.execute("""
+            DECLARE @i INT = 1;
+            WHILE @i <= 3
+            BEGIN
+                INSERT INTO #nextset_loop
+                SELECT TOP (@i) n FROM (VALUES (1), (2), (3)) AS v(n);
+                SET @i = @i + 1;
+            END;
+            """)
+        counts = [cursor.rowcount]
+        while cursor.nextset():
+            counts.append(cursor.rowcount)
+
+        assert counts == [1, 2, 3], f"Per-statement rowcounts should be [1, 2, 3], got {counts}"
+        assert sum(counts) == 6
+    finally:
+        cursor.execute("DROP TABLE IF EXISTS #nextset_loop")
+        db_connection.commit()
+
+
 def test_tables_setup(cursor, db_connection):
     """Create test objects for tables method testing"""
     try: