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_name_78 (laps INTEGER, grid VARCHAR, bike VARCHAR, rider VARCHAR)

### Question ###
What is the highest Laps, when Bike is "Yamaha YZF-R1", when Rider is "David Checa", and when Grid is greater than 18?

### Accurate SQL ###

SELECT MAX(laps) FROM table_name_78 WHERE bike = "yamaha yzf-r1" AND rider = "david checa" AND grid > 18