Dynamically set name of spool file in SQL*Plus

Small tip for today. Often there is a need to set name of spool file based on current time and might by also database you are connected to. It's often needed when script is run as scheduled task and there is a need to generate files with different names. So here is an solution for using date:

define logname=date
column clogname new_value logname
select 'prefix_'||to_char(sysdate, 'yyyymmdd') clogname from dual;
spool '&logname'

If there is a need to have also name of database included into filename then it can be read from global_name view:

define logname=date
column clogname new_value logname
select 'prefix_'||substr(global_name,1,
 decode(dot,0,length(global_name),dot-1))||
 to_char(sysdate, 'yyyymmdd') clogname
from (select global_name, instr(global_name, '.') dot from global_name);
spool '&logname'

Hope you find it useful.
I would also like to share an photo I made in Rome in February this year

To see more pictures you are welcome to follow Rome 1, Rome 2, Rome 3

Cheers, Paweł

Log Buffer #48

Welcome to 48 edition of Log Buffer. While I read Log Buffer regularly for many months already it's first time I do review of databases blogosphere. Thanks to Dave Edwards from Pythian for inviting me.

This edition will be mostly related to development tools, techniques and environments for database applications. Let start with Inside Oracle APEX where Patrick Wolf presents internals of APEX Repository. In turn Dimitri Gielis is discussing how to reuse Oracle APEX components effectively. If you still do not know what APEX is, you can begin with Oracle Application Express—What’s it All About? by Peter Lorenzen.

Jonathan Bruce at his Weblog is reviewing and recommending DataDirect Connect for ADO.NET Oracle provider for Visual Studio.
Anton Scheffer from AMIS is solving Sudoku with single SQL statement using MODEL Clause; really impressive method, I must find time to experiment with MODEL clause as it seems to be very powerful.

Linear Algebra is not commonly known feature of Oracle database. Marcos M. Campos on Oracle Data Mining and Analytics is presenting how it can be used for Principal Components Analysis and Visualization. Unfortunately complexity of examples rather will not help with wider usage of UTL_NLA package.

Jonathan Lewis on his Oracle Scratchpad presents differences in new (Oracle 10g) and old sorting algorithm. Difference is visible only for those who were using side effect of sorting by ROWID in previous oracle releases.

Jorrit Nijssen alias Jornica issued an warning on using after statement trigger and returning clause together as there is an side effect.

For many of Oracle DBAs it might be weird idea: Kevin Closson is proposing to install Oracle over NFS. He states that it's cheaper, simpler and will be even better with upcoming Oracle 11g. By the way Oracle 11g will be launched on 11th of July according to Eddie Awad. This announcement made big rumour in Oracle blogosphere and Lutz Hartmann is now documenting new feature of collecting statistics in 11g.

Laurent Schneider is discussing Best Practices for Aliasing columns in SQL queries. Dominic Delmolino on Oracle Musigns suggest another method: uniquely name columns. Also Steven Feuerstein on Toad World shows good practice: "Don't put COMMIT; in you code!".

Kevin Closson and Doug Burns discuses what is the role of Oracle, OTN, Technorati and readers for bloggers community.

Jeff of his Jeff' SQL Server Weblog that database design should not be made due to desired output. "We often see bad designs submitted at SQLTeam.com with the justification of that design being the client wanted it that way! ... you need to demonstrate to them that even when storing the data properly, we can *still* create a View which returns those exact results, making them happy".

Data Quality: Where to Validate? Beth on Confessions of a database geek is reviewing levels where validation should occur also giving some recommendations.

Roland Bouman shows What MySQL can do to enter the off-line Web. In my opinion the idea of using Web applications offline will be very hot in nearest future.
Peter Zaitsev is discussing an issue with degraded performance after upgrading MySQL 4 to MySQL 5. He also presents some workaround for that problem.
Paul McCullagh on PrimeBase XT shows how to manipulate BLOBs in MySQL using BLOB Streaming Engine.
Ronald Bradford on Technical Notes and Articles of Interest reviews Clustering solution for MySQL database.
Kevin Burton is predicting end of RAIDs . Instead he proposes to use many instances of MySQL with replication mechanism.
Xaprb announced release of MySQL Archiver 0.9.1 tool to archive content of critical OLTP tables.

JonC is answering most common Security Questions Applied to MySQL and pointing that biggest challenge is to deal with human errors. Alex Kornbrust is presenting THC Orakel new tool to Sniffer Oracle Passwords. He also points few errors in white-paper that is accompanying the tool.

Mark Rittman is on vacations leaving us with lot of BI Articles and Links to read.

Steve Jones on SQL Musings talks over High Availability of SQL Server. Euan Garden on his blog announces interesting Web Casts about new features of SQL Server 2008. While Jamie Thomson show how Group by Grouping Sets will work in Katmai: SQL Sever 2008.

Josh Berkus is reporting on JPUG 2007 PostgreSQL Conference and his keynote on "PostgreSQL Today and Tomorrow". "This was the most challenging conference for me so far since the entire conference was in Japanese, a language of which I have no comprehension."

At the and some news from my country. Jakub Pawlowski is summarizing XV PLOUG (Polish Oracle Users Group) Seminary - "Oracle Application Server 10g R3: applications, productivity, security, reliability."
That's all for today. Wait for next Log Buffer on June 15th presented by Coskan Gundogar.

Paweł

Rows to single string or aggregating strings

In oracle there is no build-in group function that will concatenate strings, just like max summarizes all numbers. But there is quite easy way to do that in pure SQL. Assume we want to have get as an query result list of tables and column. But we want all columns to be concatenated and comma separated. Result should look

TABLE_NAME	COLUMN_LIST
BLOG_LABELS	BLL_BLG_ID, BLL_LABEL
BLOG_COMMENTS	BLC_BLG_ID, BLC_IDENTIFIER, BLC_PUBLISHED_TEXT, BLC_PUBLISHED, BLC_UPDATED_TEXT, BLC_UPDATED, BLC_CONTENT, BLC_URL, BLC_AUTHOR, BLC_AUTHOR_URI
BLOG_POSTS	BLG_ID, BLG_IDENTIFIER, BLG_TITLE, BLG_PUBLISHED_TEXT, BLG_PUBLISHED, BLG_UPDATED_TEXT, BLG_UPDATED, BLG_CONTENT, BLG_URL, BLG_BGH_ID, BLG_ENTRY
BLOGS	BGH_ID, BGH_NAME, BGH_FEED_URL
FEED_CACHE	CCH_URL, CCH_TIME, CCH_VALUE

Lets start with hierarchical query to build "tree" for each table. The only one branch of this tree will start with first column and end with last one. SYS_CONNECT_BY_PATH gives as option to track that branch:

SQL> select table_name, 
  2        SYS_CONNECT_BY_PATH(column_name,  ',') column_list
  3  from user_tab_columns
  4  start with column_id = 1
  5  connect by table_name = prior table_name
  6             and column_id = prior column_id +1
  7  ;

TABLE_NAME	COLUMN_LIST
BLOGS	, BGH_ID
BLOGS	, BGH_ID, BGH_NAME
BLOGS	, BGH_ID, BGH_NAME, BGH_FEED_URL
...	...

Then I just take max path and truncating leading comma gives me expected result:

SQL> select table_name, 
  2        ltrim(max(SYS_CONNECT_BY_PATH(column_name,  ',')), ',') column_list
  3  from user_tab_columns
  4  start with column_id = 1
  5  connect by table_name = prior table_name
  6             and column_id = prior column_id +1
  7  group by table_name;

TABLE_NAME	COLUMN_LIST
BLOG_LABELS	BLL_BLG_ID, BLL_LABEL
BLOG_COMMENTS	BLC_BLG_ID, BLC_IDENTIFIER, BLC_PUBLISHED_TEXT, BLC_PUBLISHED, BLC_UPDATED_TEXT, BLC_UPDATED, BLC_CONTENT, BLC_URL, BLC_AUTHOR, BLC_AUTHOR_URI
BLOG_POSTS	BLG_ID, BLG_IDENTIFIER, BLG_TITLE, BLG_PUBLISHED_TEXT, BLG_PUBLISHED, BLG_UPDATED_TEXT, BLG_UPDATED, BLG_CONTENT, BLG_URL, BLG_BGH_ID, BLG_ENTRY
BLOGS	BGH_ID, BGH_NAME, BGH_FEED_URL
FEED_CACHE	CCH_URL, CCH_TIME, CCH_VALUE

Function Max works becouse if one string (ex.: "abc") is an prefix of the second one (ex: "abc123") than this second one is threated as bigger. I must warn that it might be not true for all NLS settings.

But what if we want columns to be ordered alphabetically? Than we have to use Row_Number function to calculate column position in table and make same changes to SQL:

SQL> select table_name, 
  2        ltrim(max(SYS_CONNECT_BY_PATH(column_name,  ',')), ',') column_list
  3  from (select table_name,  column_name,  ROW_NUMBER() OVER (partition by table_name ORDER BY column_name) AS curr  from user_tab_columns)
  4  start with curr = 1
  5  connect by table_name = prior table_name
  6             and curr = prior curr +1
  7  group by table_name;

TABLE_NAME	COLUMN_LIST
BLOG_LABELS	BLL_BLG_ID, BLL_LABEL
BLOG_COMMENTS	BLC_AUTHOR, BLC_AUTHOR_URI, BLC_BLG_ID, BLC_CONTENT, BLC_IDENTIFIER, BLC_PUBLISHED, BLC_PUBLISHED_TEXT, BLC_UPDATED, BLC_UPDATED_TEXT, BLC_URL
BLOG_POSTS	BLG_BGH_ID, BLG_CONTENT, BLG_ENTRY, BLG_ID, BLG_IDENTIFIER, BLG_PUBLISHED, BLG_PUBLISHED_TEXT, BLG_TITLE, BLG_UPDATED, BLG_UPDATED_TEXT, BLG_URL
BLOGS	BGH_FEED_URL, BGH_ID, BGH_NAME
FEED_CACHE	CCH_TIME, CCH_URL, CCH_VALUE

Hope you will find it useful and fun.
All samples where run on Oracle 10gR2 XE 10.2.0.1.
Schema used in this sample is described in Blogger Backup tool entry.

Paweł