Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_28138035_20 (mens_singles VARCHAR, mens_doubles VARCHAR)

### Question ###
How many players are there for mens singles when chen qi ma lin played mens doubles?

### Accurate SQL ###

SELECT COUNT(mens_singles) FROM table_28138035_20 WHERE mens_doubles = "Chen Qi Ma Lin"