mysql.slow_log表里记录的start_time是语句的什么时间？
答：语句的结束时间
mysql> select now(); select count(distinct url) from test order by url asc ,example desc ;
+---------------------+
| now() |
+---------------------+
| 2016-01-18 16:25:19 |
+---------------------+
1 row in set (0.00 sec)
+---------------------+
| count(distinct url) |
+---------------------+
| 199 |
+---------------------+
1 row in set (16.15 sec)
mysql> select *from mysql.slow_log order by start_time desc limit 10\G
*************************** 1. row ***************************
start_time: 2016-01-18 16:25:35
user_host: root[root] @ localhost []
query_time: 00:00:16
lock_time: 00:00:00
rows_sent: 1
rows_examined: 824832
db: test
last_insert_id: 0
insert_id: 0
server_id: 168039296
sql_text: select count(distinct url) from test order by url asc ,example desc
thread_id: 4
1 row in set (0.00 sec)
start_time为16：25：35 减去query_time: 00:00:16 等于 16:25:19
所以start_time 记录的是语句的结束时间
slow_log文件里记录的内容是
# Time: 160118 16:25:35
# User@Host: root[root] @ localhost [] Id: 4
# Query_time: 16.152763 Lock_time: 0.000102 Rows_sent: 1 Rows_examined: 824832
SET timestamp=1453105535;
select count(distinct url) from test order by url asc ,example desc;
time和timestamp 值是一样的， 都是语句的结束时间
