1.限制返回記錄的行數（4-10行）
select rownum,c1 from t144 where rownum<10
minus
select rownum,c1 from t144 where rownum<5
2.批量插入
insert into tablename(select * from othertable)
或insert into (column1,column2,,,,,,,)tablename(select column1,column2,,,,,,,from othertable)
3,分組函式(結果中出現的列要在group by 中出現)
select count(age), username, , ,... from table group by age,usename,,,,...
4.檢視資料庫中的存在的表
select table_name from dba_tables (include all users)
select * from tab(include view)
5.高效update，一次修改多個列
update smsmonitor sms
set (sms.smsmonitor_sendflag, sms.smsmonitor_maxnum) = (select s.smsmonitor_sendflag,
s.smsmonitor_maxnum
from smsmonitor s
where s.smsmonitor_id =
'i74668')
where sms.smsmonitor_id = 'i74669'
6，高效刪除表中重覆記錄
delete from emp e
where e.rowid > (select min(x.rowid)
from emp x
where x.emp_no = e.emp_no);
7.如何定位重要(消耗資源多)的sql
select sql_text
from v$sql
where disk_reads > 1000 or (executions > 0 and buffer_gets/executions > 30000);
8.如何跟蹤某個session的sql
exec dbms_system.set_sql_trace_in_session(sid,serial#,&sql_trace);
select sid,serial# from v$session where sid = (select sid from v$mystat where rownum = 1);
exec dbms_system.set_ev(&sid,&serial#,&event_10046,&level_12,'');
8，mysql中欄位操作
增加字段
alter table name add code char(200) default 0
刪除字段
alter table table_name drop column column_name
修改字段型別
alter table table_name alter column column_name new_data_type
新增主鍵字段
alter table tb add 列名 int primary key default 0
查詢被鎖住的sql語句
select /*+ rule */ s.username,
decode(l.type,'tm','table lock',
'tx','row lock',
null) lock_level,
o.owner,o.object_name,o.object_type,
s.sid,s.serial#,s.terminal,s.machine,s.program,s.osuser
from v$session s,v$lock l,dba_objects o
where l.sid = s.sid
and l.id1 = o.object_id(+)
and s.username is not null
解鎖表--alter system kill session 'sid,serial#';
--把鎖給kill掉
alter system kill session '146,21177';
解鎖使用者sql
alter user username account unlock;
根據索引名稱查詢該索引所在的表資訊
select table_name from all_indexes where index_name='dchnbaccfeedet_pk'
查詢該索引的資訊
select * from all_objects where object_name like 'dchnbaccfeedet_pk'
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