Task: Text to Code
Input (English): Step 1: find the number of rows of each value of document_type_code in Documents table.
Step 2: find document_type_code of Documents table ordered descending by the results of step 1.
Step 3: only show the first 3 rows of the results
Output (English): SELECT document_type_code FROM Documents GROUP BY document_type_code ORDER BY Count ( * ) Desc LIMIT 3