这个查询首先得理解dba_hist_sqlstat视图，也就是并不是所有SQL都在dba_hist_sqlstat里都能查询：
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DBA_HIST_SQLSTAT displays historical information about SQL statistics. This view captures the top SQL statements based on a set of criteria and captures the statistics information from V$SQL. The total value is the value of the statistics since instance startup. The delta value is the value of the statistics from the BEGIN_INTERVAL_TIME to the END_INTERVAL_TIME in the DBA_HIST_SNAPSHOT view.
ELAPSED_TIME_DELTA：
Delta value of elapsed time (in microseconds) used by this cursor for parsing/executing/fetching
select a.sql_text SQL语句,
b.etime 执行耗时,
c.user_id 用户ID,
c.SAMPLE_TIME 执行时间,
c.INSTANCE_NUMBER 实例数,
u.username 用户名, a.sql_id SQL编号
from dba_hist_sqltext a,
(select sql_id, ELAPSED_TIME_DELTA / 1000000 as etime
from dba_hist_sqlstat
where ELAPSED_TIME_DELTA / 1000000 >= 1) b,
dba_hist_active_sess_history c,
dba_users u
where a.sql_id = b.sql_id
and u.username = 'MYDB'
and c.user_id = u.user_id
and b.sql_id = c.sql_id
and a.sql_text like '%XXX%'
order by SAMPLE_TIME desc,
b.etime desc;