@Override
    public String getTableAlias() {
        //there is different between getFrom() and getTableSource()
        //when use "delete t1 from t t2", getTableSource().getAlias() will return null
        if (ast.getFrom() == null) {
            return ast.getTableSource().getAlias();
        }
        return ast.getFrom().getAlias();
    }
@Test
    public void testGetTableAlias() {
        String sql = "DELETE FROM t WHERE id = ?";
        SQLStatement ast = getSQLStatement(sql);

        SqlServerDeleteRecognizer recognizer = new SqlServerDeleteRecognizer(sql, ast);
        Assertions.assertNull(recognizer.getTableAlias());

        sql = "DELETE t1 FROM t t1 WHERE t1.id = ?";
        ast = getSQLStatement(sql);

        recognizer = new SqlServerDeleteRecognizer(sql, ast);
        Assertions.assertEquals("t1", recognizer.getTableAlias());
    }