PL/SQL bulk collect union

PL/SQL bulk collect will work with UNION ALL when written with an inline view:

   l_big l_type_assoc ;
     WITH q AS (
          SELECT ename AS name
            FROM emp
           UNION ALL
          SELECT dname AS name
            FROM dept
   SELECT name
     FROM q
    ORDER BY name ;

   FOR indx IN 1..l_big.COUNT
      DBMS_OUTPUT.put_line ( l_big(indx) ) ;


If the array you are using is not an associative array (that is, does not have the INDEX BY clause in its declaration) then an alternative method is to merge arrays together after they are populated with multiset union:

   TYPE l_type_varray IS TABLE OF VARCHAR2(14) ;
   l_tmp l_type_varray ;
   l_big l_type_varray ;

   SELECT ename BULK COLLECT INTO l_tmp FROM emp ;

   l_big := l_tmp ;  -- copy the array

   SELECT dname BULK COLLECT INTO l_tmp FROM dept ;

   l_big := l_big MULTISET UNION ALL l_tmp ;  -- union the arrays

   FOR indx IN 1..l_big.COUNT
      DBMS_OUTPUT.put_line ( l_big(indx) ) ;


PHP’s oci_bind_array_by_name will only work with associative arrays, returns error ‘ORA-06550: PLS-00306: wrong number or types of arguments in call’ if varrays are used.

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Extended Hexadecimal in Oracle

Standard decimal > hexadecimal is done with:

select to_char ( 10 , 'x' ) from dual ;

But I wanted a kind of extended hexadecimal that would keep single letters going up beyond 15/f, so would return ‘g ‘for decimal 16 instead of returning hexadecimal ’10′.

Why did I want that? I needed to squeeze a 2 digit number column into a 1 character column in an extract transform load operation. Most of the source data was less than 16, but there were a few values higher than that, and a simple decimal > hexadecimal translation wouldn’t work for those.

The ascii value for ‘a’ is 97, so using the chr function to turn numbers into their ascii character equivalents gives:

           WHEN numcol BETWEEN  0 AND  9 THEN TO_CHAR ( numcol )
           WHEN numcol BETWEEN 10 AND 35 THEN CHR ( 87 + numcol )
       END AS extended_hexadecimal
  FROM mytable ;
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srvctl start listener -n nodename

Preferred method to stop and start oracle listener in RAC enivronment:

srvctl config listener -n nodename
srvctl stop listener -n nodename
srvctl start listener -n nodename
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Denormalise listagg children on single row comma separated

You can denormalise data using the listagg function, so to display users with their roles on a single line comma separated:

SELECT grantee
     , LISTAGG ( granted_role , ' , ' ) WITHIN GROUP ( ORDER BY granted_role ) AS granted_roles
  FROM dba_role_privs
 GROUP BY grantee

H/t Adrian Billington. Continue reading

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Oracle remove duplicates parent child with listagg

De-duplicating parent – child table sets of data here using the listagg function to merge all the child rows into a single denormalised column.

set serverout on
FOR d1 IN (
     WITH denorm AS (
          SELECT parent.aos_code
               , parent.pre_group_id
               , LISTAGG ( child.aos_code || child.stud_pass ) WITHIN GROUP ( ORDER BY child.aos_code || child.stud_pass ) AS entry_value
            FROM StcAPreList parent
            JOIN StcAPreGroupAos child
              ON parent.pre_group_id = child.pre_group_id
           GROUP BY parent.aos_code , parent.pre_group_id
   SELECT a.pre_group_id
     FROM denorm a
    WHERE a.pre_group_id > (
          SELECT MIN ( b.pre_group_id )
            FROM denorm b
           WHERE a.aos_code = b.aos_code
             AND a.entry_value = b.entry_value )
    ORDER BY 1
   dbms_output.put_line ( 'deleting ' || d1.pre_group_id ) ;
   DELETE FROM StcAPreGroupAos child WHERE child.pre_group_id = d1.pre_group_id ;
   DELETE FROM StcAPreList parent WHERE parent.pre_group_id = d1.pre_group_id ;
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Create output XML data files from oracle with dbms_xmlgen

The below code will generate XML format output, just plug in any SQL and it will work without further development.

This is based on three articles by other authors:

  • Tim Hall – but Tim’s code has a bug that stops it outputting after the first 32k of data.
  • Tom Kyte – the fix for that bug.
  • Steve Karam – code to nest XML data.

Performance is kept optimal by using set based SQL statements without cursor loops, and by using utl_file.put to write in 32k chunks rather than line-by-line of dbms_output.put_line or utl_file.put_line.

Before generating XML, ask if this is the best approach for transferring the data. Database to database copying is better done across database link, if possible.

Code: Continue reading

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Replace all tnsnames.ora files with a single master file using TNS_ADMIN

Maintaining large numbers of client tnsnames.ora files is a pain.  Oracle Internet Directory is the recommended solution to this, but it is not an easy exercise to set up or migrate to.

An easier alternative is to set TNS_ADMIN in all client PCs to use a single common tnsnames.ora file

set TNS_ADMIN=\\network\share\path

All the client PCs need read access to that file, but don’t need write access.
One drawback of doing that is that if the network share is unavailable for any reason then all client connections will fail, so a highly resilient network share would be needed. A safer alternative is to set TNS_ADMIN to the same local disk folder on each PC

set TNS_ADMIN=C:\SecureITFolder

and rely on automated PC management tools like Microsoft System Centre to deploy the master tnsnames file out to each client PC at regular intervals.

The precedence of TNS_ADMIN in Windows is supposedly (I’ve not yet tested this):

  1. In current working directory
  2. TNS_ADMIN defined by the session (set tns_admin= in batch/command prompt)
  3. TNS_ADMIN defined as a global environment variable (control panel > system > advanced system settings > advanced > environment variables)
  4. TNS_ADMIN defined in registry (run “regedit” and look under HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\…)
  5. Default location (network\admin directory for that particular Oracle Home)
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Copy mirror files with robocopy rsync lftp

The best utilities to use when copying/mirroring/backing up files are:

  • robocopy – Windows
  • rsync – Linux
  • lftp – Linux without setting up password-less ssh

Scripts can supply a password to sftp using lftp like this:

lftp -u user:password s << END_LFTP  
put /directory/file.txt  

You can set up password-less ssh this way.

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Shrink Transaction Logs in all every database SQL Server

SQL Server transaction logs need backed up regularly, or they will grow and grow forever, eventually filling up all available disk space. That is best done in a maintenance plan. Unfortunately you have to remember to set that up post install, it doesn’t happen out of the box by default (why doesn’t it? Surely it would be easy for Microsoft to create a standard maintenance plan at install time?).

Oracle does’t have this problem, its redo logs are a fixed size and are automatically archived off by default

If you have a SQL Server that has been left unattended like this for a long time, you may want to shrink down the over-large transaction log files in addition to setting up a maintenance plan – although that can cause fragmentation so you might also choose to leave it be.

To shrink use commands like these:
Continue reading

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Remote Desktop Connection Manager

Remote Desktop Connection Manager, a free download from, lets you switch quickly between windows servers, saves the servers and your login details in a list.

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