根据某个字段去重根据另一个字段排序的一个SQL

背景：
一张表有 name , crt_time , work_sts 三个字段

这张表里存在这样的数据

\'a\', \'2018-12-18 21:37:24\', \'未\'
\'a\', \'2018-12-19 09:37:24\', \'完\'
\'a\', \'2018-12-19 21:37:24\', \'未\'
\'b\', \'2018-11-18 21:37:24\', \'完\'
\'b\', \'2018-11-19 20:37:24\', \'完\'
\'b\', \'2018-11-20 09:37:24\', \'完\'
\'c\', \'2018-11-18 21:47:24\', \'完\'
\'c\', \'2018-11-19 20:57:24\', \'完\'
\'c\', \'2018-11-20 09:33:24\', \'未\'
\'d\', \'2018-12-18 21:17:24\', \'未\'
\'d\', \'2018-12-19 09:17:24\', \'完\'
\'d\', \'2018-12-19 21:17:24\', \'完\'

现在需要根据 name 去重要求如下：
1. 同一个name下 work_sts没有未的时候取完数据里 crt_time 最大的那条数据
2. 同一个name下 work_sts有一个未取未这条数据
3. 同一个name下 work_sts有多个未取未数据里 crt_time 最大的那条数据

答案：

SELECT a.*
FROM t_test a
JOIN(
SELECT col1,MAX(col2) col2
FROM t_test
WHERE col3=\'未\'
GROUP BY col1
HAVING SUM(IF(col3=\'未\',1,0)) > 0
)b
WHERE a.col1 = b.col1 AND a.col2 = b.col2
UNION
SELECT a.*
FROM t_test a
JOIN (
SELECT col1,MAX(col2) col2
FROM t_test
GROUP BY col1
HAVING SUM(IF(col3=\'未\',1,0)) = 0
)c
WHERE a.col1 = c.col1 AND a.col2 = c.col2
ORDER BY col1

CREATE TABLE `t_test` (
  `col1` varchar(32) DEFAULT NULL COMMENT \'col1\',
  `col2` varchar(128) DEFAULT NULL COMMENT \'col2\',
  `col3` varchar(64) DEFAULT NULL COMMENT \'col3\',
  `id` varchar(30) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8


INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'a\', \'2018-12-18 21:37:24\', \'未\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'a\', \'2018-12-19 09:37:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'a\', \'2018-12-19 21:37:24\', \'未\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'b\', \'2018-11-18 21:37:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'b\', \'2018-11-19 20:37:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'b\', \'2018-11-20 09:37:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'c\', \'2018-11-18 21:47:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'c\', \'2018-11-19 20:57:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'c\', \'2018-11-20 09:33:24\', \'未\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'d\', \'2018-12-18 21:17:24\', \'未\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'d\', \'2018-12-19 09:17:24\', \'归\', \'100\');
INSERT INTO `t_test` (`col1`, `col2`, `col3`, `id`) VALUES (\'d\', \'2018-12-19 21:17:24\', \'归\', \'100\');