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_20186 ( "Class" text, "Wheel Arrangement" text, "Railway" text, "Number at Doncaster" real, "Number at Pyewipe" real, "Number at March" real )

### Question ###
Name the number at march when class is j66

### Accurate SQL ###

SELECT "Number at March" FROM table_20186 WHERE "Class" = 'J66'