如何将这个Simple SQLServer语句转换为MySQL语句？

Question

给定一个包含3列的表：C1，C2，C3

C1 - C2 - C3
M  - is - M1
N2 - is - N3
M2 - is - M3
M3 - is - M4
N1 - is - N2
M1 - is - M2
N  - is - N1

如何将此Simple SQLServer语句转换为MySQL语句：

declare @searchString varchar(32) = 'M';
with cte(results) as
(
    select C3 from Tbl where C1 = @searchString
    union all
    select t.C3 from Tbl t inner join cte c on c.C3 = t.C1 
) select * from cte;