兄弟，是否是遇到过查询 V$SESSION.SQL_ID 但是呢 SQL_ID 是空，然后找不到SQL的为难情况？太多人问这个问题了。
我相信你们也没百度/GOOGLE到好的解决办法，今天就分享1个方法，教大家抓SQL(本方法基于ORACLE11G，10G 就洗洗睡吧)。
首先我们来做个实验：
SQL> select sid from v$mystat where rownum=1;
SID
----------
1150
SQL> update test set owner='BIGSB' where object_id<100;
98 rows updated
在1150这个SESSION里面履行1个UPDATE，不要提交。
SQL> select sid from v$mystat where rownum=1;
SID
----------
1338
SQL> update test set owner='SB' where object_id<10;
在1338里面跑另外1个UPDATE，由于1150没提交，1138处于行锁等待。
这个时候通过以下脚本去查询数据库：
SQL> select inst_id,
2 sid,
3 sql_id,
4 event,
5 blocking_session,
6 blocking_instance
7 from gv$session a
8 where blocking_session is not null;
INST_ID SID SQL_ID EVENT BLOCKING_SESSION BLOCKING_INSTANCE
---------- ---------- ------------- --------------------------------------- ---------------- ----------------
1 1338 852mvmth18w37 enq: TX - row lock contention 1150 1
SQL> select sql_id from gv$session where inst_id=1 and sid=1150;
SQL_ID
-------------
确切，SQL_ID是空的，或许有人会说，那我去查询PREV_SQL_ID，恩你去试1试吧，那个SQL_ID是事物的SQL_ID，其实不是UPDATE的SQL_ID
SQL> select prev_sql_id from gv$session where inst_id=1 and sid=1150;
PREV_SQL_ID
-------------
9m7787camwh4m
SQL> select sql_text from gv$sql where sql_id='9m7787camwh4m';
SQL_TEXT
--------------------------------------------------------------------------------
begin :id := sys.dbms_transaction.local_transaction_id; end;
所以很多人这个时候就蛋疼了，不知道咋办。现在教大家另外1种方法
SQL> select PREV_EXEC_START,USERNAME,MODULE,ACTION FROM GV$SESSION WHERE INST_ID=1 AND SID=1150;
PREV_EXEC_START USERNAME MODULE ACTION
--------------- ------------------------------ -----------------------
2015-04⑴0 18:01:44 SCOTT PL/SQL Developer Command Window - New
SQL> SELECT SQL_ID,SQL_TEXT,LAST_ACTIVE_TIME,MODULE,ACTION FROM GV$SQL WHERE INST_ID=1 AND LAST_ACTIVE_TIME=TO_DATE('2015-04⑴0 18:01:44','YYYY-MM-DD HH24:MI:SS');
SQL_ID SQL_TEXT LAST_ACTIVE_TIME MODULE ACTION
------------- -------------------------------------------------------------------------------- ---------------- ---------------------------------------------------------------- ----------------------------------------------------------------
2syvqzbxp4k9z select u.name, o.name, a.interface_version#, o.obj# from association$ a, us 2015/4/10 18:01:
6c9wx6z8w9qpu select a.default_selectivity from association$ a 2015/4/10 18:01:
2xyb5d6xg9srh select a.default_cpu_cost, a.default_io_cost from association$ a 2015/4/10 18:01:
d1s917pgj7650 update test set owner='BIGSB' where object_id<100 2015/4/10 18:01: PL/SQL Developer Command Window - New
现在就能够把SQL 抓到了
请注意：
1.在高并发的情况下，可能会出现多个可疑SQL
2.LAST_ACTIVE_TIME与PREV_EXEC_START可能有小的误差(秒计)
这个时候，请自己判断，脑袋不要太笨。
select a.inst_id, a.sid, a.sql_id, b.sql_id, b.sql_text
from gv$session a, gv$sql b
where a.inst_id = b.inst_id
and a.PREV_EXEC_START = b.LAST_ACTIVE_TIME
and a.USERNAME = b.PARSING_SCHEMA_NAME
and a.MODULE_HASH = b.MODULE_HASH
and a.ACTION_HASH = b.ACTION_HASH
select a.inst_id,
a.sid,
a.event,
a.sql_id,
b.sql_text running_sql,
c.sql_in_session,
c.sql_id_in_v$sql,
c.sql_text blocking_sql,
a.blocking_session,
a.blocking_instance
from gv$session a,
(select sql_id, sql_text
from (select sql_id,
sql_text,
row_number() over(partition by sql_id order by sql_id) as rn
from gv$sql)
where rn = 1) b,
(select a.inst_id,
a.sid,
a.sql_id sql_in_session,
b.sql_id sql_id_in_v$sql,
b.sql_text
from gv$session a, gv$sql b
where a.inst_id = b.inst_id
and a.PREV_EXEC_START =b.LAST_ACTIVE_TIME
and a.USERNAME = b.PARSING_SCHEMA_NAME
and a.MODULE_HASH = b.MODULE_HASH
and a.ACTION_HASH = b.ACTION_HASH) c
where a.sql_id = b.sql_id
and a.blocking_session is not null
and a.BLOCKING_SESSION = c.sid
and a.BLOCKING_INSTANCE = c.inst_id;
??