sql小结(1)
//在crud中调用函数 select Func_getUTCDate() from dual;------------------------------------------------------------------------------------------//oracle的分页select * from (select t. * , rownum as linenumfromt_person t where rownum < 10 ) where linenum > 4;select * from T_person t where t.fatherid = 0 connect by prior t.id = t.fatherid;------------------------------------------------------------------------------------------ //创建临时表 create global temporary table temp_tbl(col_a varchar2(30)) on commit delete rowscreate global temporary table temp_tbl(col_a varchar2(30)) on commit preserve rows ------------------------------------------------------------------------------------------ alter system kill session 'sid,serial#';select * from v$session where username= upper('scott');------------------------------------------------------------------------------------------//decode的高级版本 select (case when 10> 5 then 'ok' when 10=5 then 'fail' else 'lll' end) from dual;一个汉字在oracle中是占用了两个字节的。 英文字母或符号只占用一个字节。 Char(10)最多可存放5个汉字。------------------------------------------------------------------------------------------create materialized view t_user_money refresh start with sysdate next sysdate + 5/1440 with rowid as select username, money from t_u_money@UMLink;commit;------------------------------------------------------------------------------------------手动刷新快照 begin dbms_refresh.refresh('"CS"."SN_ANSON"'); end; ------------------------------------------------------------------------------------------//第一种方法(这也是默认的方法on demand) create materialized view test_viewrefreshforce on demand start with sysdate next sysdate + 1/1440 --(注意)系统会自动创建job,每分钟更新一次 as select * from emp;//第二种方法 create materialized view test_viewrefreshforce on commitas select * from emp;------------------------------------------------------------------------------------------//自定义补充的格式 SQL>select lpad ( 'xuxu',20,'*') from dual;LPAD('DAGA',20,'*')--------------------****************xuxu------------------------------------------------------------------------------------------0是一个特殊的值，它在oracle中存储为128.//手工删除物理上的db文件后，造成启动失败处理如下：alter database datafile '/opt/oracle/oradata/lbs8.dbf'offline drop;//字符串，从1开始，左包括select t.*, t.rowid from t_task t order by to_number(substr(t.id,5));最高效的删除重复记录方法 ( 因为使用了ROWID)例子： DELETE FROM EMP EWHERE E.ROWID > (SELECT MIN(X.ROWID) FROM EMP X WHERE X.EMP_NO = E.EMP_NO);select substr('hello',0,3) from dual;和select substr('hello',1,3)from dual ;相同-------------------------------------------------------------------------------------------SQL> select * from user_role_privs;USERNAME GRANTED_ROLE ADMIN_OPTION DEFAULT_ROLE OS_GRANTED---------------- ------------------ ------------ ------------ ----------SCOTT CONNECT NO YES NOshow parameter;//显示oracle的系统参数select * from v$version;alter user scott account unlock;//查看表空间的freeselect * from dba_free_space;#显示每条sql语句占用的内存select sql_text ,sharable_mem from v$sql where sharable_mem > '100000' order by sharable_mem ;select * from v$sgastat; --显式SGA的状态信息。
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