--578. Get Highest Answer Rate Question

--

--Get the highest answer rate question from a table survey_log with these columns: uid, action, question_id, answer_id, q_num, timestamp.

--

--uid means user id; action has these kind of values: "show", "answer", "skip"; answer_id is not null when action column is "answer", while is null for "show" and "skip"; q_num is the numeral order of the question in current session.

--

--Write a sql query to identify the question which has the highest answer rate.

--

--Example:

--Input:

-- ------ ----------- -------------- ------------ ----------- ------------

--| uid | action | question_id | answer_id | q_num | timestamp |

-- ------ ----------- -------------- ------------ ----------- ------------

--| 5 | show | 285 | null | 1 | 123 |

--| 5 | answer | 285 | 124124 | 1 | 124 |

--| 5 | show | 369 | null | 2 | 125 |

--| 5 | skip | 369 | null | 2 | 126 |

-- ------ ----------- -------------- ------------ ----------- ------------

--Output:

-- -------------

--| survey_log |

-- -------------

--| 285 |

-- -------------

--Explanation:

--question 285 has answer rate 1/1, while question 369 has 0/1 answer rate, so output 285.

--Note: The highest answer rate meaning is: answer number's ratio in show number in the same question.

SELECT question_id AS 'survey_log' FROM survey_log GROUP BY question_id ORDER BY

COUNT(answer_id) / COUNT(case when survey_log.action =

'show' then survey_log.action else null end) DESC LIMIT 0,1