BUG: read_sql wraps plain SQL strings in sqlalchemy.text() to allow % modulo and LIKE patterns (#35484)

pandas/io/sql.py

@@ -98,7 +98,30 @@
 # -- Helper functions
 
 
+def _sa_text_if_string(stmt: Any) -> Any:
+    """
+    Wrap plain SQL strings with sqlalchemy.text() if SQLAlchemy is available.
+
+    Parameters
+    ----------
+    stmt : Any
+        The SQL statement or object.
+
+    Returns
+    -------
+    Any
+        `sqlalchemy.sql.elements.TextClause` if wrapping occurred,
+        otherwise the original statement.
+    """
+    try:
+        import sqlalchemy as sa  # lazy import; keep SA optional
+    except ImportError:
+        return stmt
+    return sa.text(stmt) if isinstance(stmt, str) else stmt
+
+
 def _process_parse_dates_argument(parse_dates):
+
     """Process parse_dates argument for read_sql functions"""
     # handle non-list entries for parse_dates gracefully
     if parse_dates is True or parse_dates is None or parse_dates is False:
@@ -1853,7 +1876,8 @@ def read_query(
         read_sql
 
         """
-        result = self.execute(sql, params)
+        stmt = _sa_text_if_string(sql)
+        result = self.execute(stmt, params)
         columns = result.keys()
 
         if chunksize is not None:
@@ -1882,6 +1906,7 @@ def read_query(
             )
             return frame
 
+
     read_sql = read_query
 
     def prep_table(

pandas/tests/io/sql/test_percent_patterns.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+from typing import Any
+
+import pytest
+
+pytest.importorskip("sqlalchemy")
+
+
+def test_modulo_operator(sql_con: Any) -> None:
+    query = "SELECT 10 % 3"
+    result = sql_con.execute(query)
+    assert result.scalar() == 1
+
+
+def test_like_pattern(sql_con: Any) -> None:
+    query = "SELECT 'abc' LIKE 'a%'"
+    result = sql_con.execute(query)
+    assert result.scalar() == 1
+
+
+def test_sqlalchemy_selectable(sql_con: Any) -> None:
+    from sqlalchemy import literal, select
+
+    stmt = select(literal("hello"))
+    result = sql_con.execute(stmt)
+    assert result.scalar() == "hello"