参考：
https://www.jb51.net/article/129656.htm
DELETE testcase
FROM
testcase,
(
SELECT
max(id) id,
api_purpose,
api_host,
request_url,
request_data,
assert_method,
check_point,
correlation,
active,
creater
FROM
testcase
GROUP BY
api_purpose,
api_host,
request_url,
request_data,
assert_method,
check_point,
correlation,
active,
creater
HAVING
count(*) > 1
) t2
WHERE
testcase.api_purpose = t2.api_purpose
and testcase.api_purpose = t2.api_purpose
and testcase.api_host = t2.api_host
and testcase.request_url = t2.request_url
and testcase.request_data = t2.request_data
and testcase.assert_method = t2.assert_method
and testcase.check_point = t2.check_point
and testcase.correlation = t2.correlation
and testcase.active = t2.active
and testcase.creater = t2.creater
and testcase.id <t2.id;