fix: Use of HAVING outside of GROUP BY should raise a suitable SQ…

…LSyntaxError

crates/polars-sql/src/context.rs

@@ -709,6 +709,11 @@ impl SQLContext {
         };
 
         lf = if group_by_keys.is_empty() {
+            // The 'having' clause is only valid inside 'group by'
+            if select_stmt.having.is_some() {
+                polars_bail!(SQLSyntax: "HAVING clause not valid outside of GROUP BY; found:\n{:?}", select_stmt.having);
+            };
+
             // Final/selected cols, accounting for 'SELECT *' modifiers
             let mut retained_cols = Vec::with_capacity(projections.len());
             let have_order_by = query.order_by.is_some();

py-polars/tests/unit/sql/test_group_by.py

@@ -238,3 +238,9 @@ def test_group_by_errors() -> None:
         match=r"'a' should participate in the GROUP BY clause or an aggregate function",
     ):
         df.sql("SELECT a, SUM(b) FROM self GROUP BY b")
+
+    with pytest.raises(
+        SQLSyntaxError,
+        match=r"HAVING clause not valid outside of GROUP BY",
+    ):
+        df.sql("SELECT a, COUNT(a) AS n FROM self HAVING n > 1")