DBA常用sql(二)
session状态：
STATUS VARCHAR2(8) Status of the session:
ACTIVE - Session currently executing SQL
INACTIVE - sql及其session没有释放或正常退出......
KILLED - Session marked to be killed
CACHED - Session temporarily cached for use by Oracle*XA
SNIPED - Session inactive, waiting on the client
查询数据库中持锁和等待锁的用户信息
select distinct o.object_name, sh.sid "SID", sh.SERIAL# "SERIAL", sh.username||'('||sh.sid||','||sh.SERIAL#||')' "Holder",
sw.username||'('||sw.sid||','||sw.SERIAL#||')' "Waiter",
decode(lh.lmode, 1, 'null', 2,
'row share', 3, 'row exclusive', 4, 'share',
5, 'share row exclusive' , 6, 'exclusive') "Lock Type"
from v$session sw, v$lock lw,all_objects o, v$session sh, v$lock lh
where lh.id1 = o.object_id
and lh.id1 = lw.id1
and sh.sid = lh.sid
and sw.sid = lw.sid
and sh.lockwait is null
and sw.lockwait is not null
and lh.type = 'TM'
and lw.type = 'TM';
select /*+ NO_MERGE(a) NO_MERGE(b) NO_MERGE(c) */ 'Wait' "Status", a.username, a.machine, a.sid, a.serial#, a.last_call_et "Seconds", b.id1, c.sql_text "SQL"
from v$session a, v$lock b, v$sqltext c
where a.username is not null
and a.lockwait = b.kaddr
and c.hash_value =a.sql_hash_value
union
select /*+ NO_MERGE(a) NO_MERGE(b) NO_MERGE(c) */ 'Lock' "Status", a.username, a.machine, a.sid, a.serial#, a.last_call_et "Seconds", b.id1, c.sql_text "SQL"
from v$session a, v$lock b, v$sqltext c
where b.id1 in
(select /*+ NO_MERGE(d) NO_MERGE(e) */ distinct e.id1
from v$session d, v$lock e
where d.lockwait = e.kaddr)
and a.username is not null
and a.sid = b.sid
and b.request=0
and c.ha
相关文档：
ms sql 更新表A中某列为表B中的值
select *
from dbo.NT_areapin
go
select *
from dbo.NT_dict_area
update NT_areapin
set AllNamePin='PengShui'
from NT_areapin
where AreaId='486'
go
update NT_dict_area
set BriefNamePin = NT_areapin.BriefNamePin,AllNamePin = NT_areapin.AllNamePin
from N ......
为了大家更容易理解我举出的SQL语句，本文假定已经建立了一个学生成绩管理数据库，全文均以学生成绩的管理为例来描述。
1.在查询结果中显示列名：
a.用as关键字：select name as '姓名' from students order by age
b.直接表示：select name '姓名' from students order by age
2.精确查找:
a.用 ......
方法一：
select distinct name from tablename
方法二：
select min(fid),name,sex from tablename group by name
总计：
select distinct name from tablename 打开重复记录的单个字段
select * from tablename where fid in(Select min(fid) from tablename group by name)打开重复记录的所有字段值
select ......
为了研究一下系统在后台都干了什么，当然是我在代码里没找到的情况下，研究了一下trace，结果有一定的帮助。oracle中不像sql server中那样直接提供图像化的工具，所以还是得自己动手来做，归纳了一下，步骤如下：
查询session：
SQL> select sid, serial#, username from v$session where username='XXX';//找出你要跟 ......
---------数学函数
1.绝对值
S:select abs(-1) value
O:select abs(-1) value from dual
2.取整(大)
S:select ceiling(-1.001) value
O:select ceil(-1.001) value from dual
3.取整（小）
S:select floor(-1.001) value
O:select floor(-1.001) value from dual
4.取整（截取）
S:select cast(-1.002 as int) v ......
