Oct 29, 2010

To get only numeric values

To  retrieve only numeric values from both numeric& character value

In 10 g

Select  regexp_replace(regexp_replace('5RTYDDB','([[:punct:]])'),'([[:alpha:]])')
  from dual t 
 
In 9i  
 
 select replace('BBd3',TRANSLATE('BBd3', ' +-.0123456789', ' '),'') from dual

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Oct 18, 2010

DBMS_WM.CompressWorkspace

DBMS_WM.Compress Workspace

 If   you version enabled the tables with  DBMS_WM.EnableVersioning ('TABLE_NAME', 'VIEW_WO_OVERWRITE')   API  THEN your  Oracle Workspace  database WILL  GET SLOW  WHEN SO MANY DATA COMES ; use DBMS_WM.CompressWorkspace API  TO MAKE IT FASTER; There is a scenario to check  whether your Workspace  is getting slow or Workspace database is to be Compressed or not ,execute this  workspace API
DBMS_WM.SetDiffVersions('LIVE',wksp2) . and  then  pick a version enabled table having highest record count   , issue command select count(*) from tablename_diff ; if it takes more than a minute to GET RESULT THEN YOU CAN MAKE SURE THAT YOU NEED TO COMPRESS YOUR WORKSPACE ;here u want to use the   statement  (1) , using statement (2) will not give better result because your table is version enabled  with DBMS_WM.EnableVersioning ('TABLE_NAME', 'VIEW_WO_OVERWRITE')  .

(1) exec DBMS_WM.CompressWorkspace('LIVE',compress_view_wo_overwrite => true);

(2) exec DBMS_WM.CompressWorkspace('LIVE')



VIEW_WO_OVERWRITE: The without overwrite (WO_OVERWRITE) option. A view named _HIST  is created to contain history information, and it will show all modifications to the same version of the table. A history of modifications to the version is maintained; that is, subsequent changes to a row in the same version do not overwrite earlier changes.

compress_view_wo_overwrite        A Boolean value (TRUE or FALSE).

TRUE causes history information between the affected savepoints to be deleted even if VIEW_WO_OVERWRITE was specified when versioning was enabled.

FALSE causes history information (between the affected savepoints) for a table not to be deleted if VIEW_WO_OVERWRITE was specified when versioning was enabled. (If VIEW_WO_OVERWRITE was not specified for a table, history information for the table is deleted regardless of the parameter value.) FALSE is assumed if the procedure format without this parameter is used.


Advantage
------------
1  Run-time performance for Workspace Manager operations is improved.
2  Less disk storage is used for Workspace Manager structures

Oct 13, 2010

Use of Combined Index

The Below example shows the difference in execution plan when a composite index is created  

SELECT d.ITEM_ID,d.ITEM_DESC,D.UNIT,d.ITEM_REF_ID,d.ITEM_LEVEL,N_QTYMILE,S_WORKCODE,
SYS_CONNECT_BY_PATH (ITEM_DESC,'--->') scbdesc,LPAD(' ',level*3,' ')||ITEM_DESC LNAME ,ACCESSORIES,SYS_CONNECT_BY_PATH (ITEM_ID,'--->') scbp,level,CONNECT_BY_ROOT ITEM_ID rootn , CONNECT_BY_ISLEAF leaf FROM ITEM_MASTER d START WITH ITEM_REF_ID is null CONNECT BY PRIOR ITEM_ID =ITEM_REF_ID ORDER SIBLINGS BY ITEM_LEVEL



create index idx_ITEM_MASTER_refid  on ITEM_MASTER (ITEM_ID,ITEM_REF_ID)

After creating combined index check the execution plan




SELECT  d.ITEM_ID,d.ITEM_DESC,D.UNIT,d.ITEM_REF_ID,d.ITEM_LEVEL,N_QTYMILE,S_WORKCODE,
SYS_CONNECT_BY_PATH (ITEM_DESC,'--->') scbdesc,LPAD(' ',level*3,' ')||ITEM_DESC LNAME ,ACCESSORIES,SYS_CONNECT_BY_PATH (ITEM_ID,'--->') scbp,level,CONNECT_BY_ROOT ITEM_ID rootn , CONNECT_BY_ISLEAF leaf FROM ITEM_MASTER d
START WITH ITEM_REF_ID is  null CONNECT BY PRIOR ITEM_ID =ITEM_REF_ID ORDER SIBLINGS BY ITEM_LEVEL