DATE with BASH Shell

Was struggling to get date validated in linux ... writing a script with all that date parsing checks (valid day, month etc.) naah there mus be some easy way, something that is built in. The OS itself manages date and time so it should have the logic built in. Why not leverage it.

Came across this date command in shell, which is designed to handle relative date calculations and return/print them to you in a user defined way.

Everyone is familiar with the $ date command

cmd:   $ date
result:  Tue May 14 07:47:45 IST 2013 


Now getting the previous day
cmd:   $ date --date="yesterday"
result:  Tue May 13 07:50:35 IST 2013 



Now getting the next day

cmd:   $ date --date="next day"
result:  Tue May 15 07:50:55 IST 2013 

Looks  great isn't it and not only this one can use different string formats to get the same output
Example

cmd:   $ date --date="1 days ago"   or
cmd:   $ date --date="1 day ago"  or
cmd:   $ date --date="-1 day"    or
cmd:   $ date --date="yesterday"    
result:  Tue May 13 07:50:35 IST 2013

Example of various string formats is
Past:
cmd:   $ date --date="yesterday"
cmd:   $ date --date="20 minute ago"
cmd:   $ date --date="2 hour ago"
cmd:   $ date --date="last Friday"
cmd:   $ date --date="10 days ago"
cmd:   $ date --date="10 week ago"
cmd:   $ date --date="10 month ago"

Future:
cmd:   $ date --date="tommorrow"
cmd:   $ date --date="20 minute"
cmd:   $ date --date="2 hour"
cmd:   $ date --date="this Friday"
cmd:   $ date --date="10 days "
cmd:   $ date --date="10 week"
cmd:   $ date --date="10 month "

Its amazing... very nicely coded and not only this you can specify your custom date format

cmd:   $ date --date="tommorrow" + "%d/%m/%Y"

Hope you find it interesting and helpful too..

Have a nice time playing with your dates. -S

UPDATE .. FROM syntax difference in Sql Server and Oracle

There is syntactical difference in few operations in SQL in Oracel and Sql server

For example: UPDATE .. FROM

UPDATE students

     SET grade='A'

FROM students s 

INNER JOIN students_marks sm ON sm.student_id = s.student_id

WHERE sm.total_marks>80;

The above query syntax works in Sql Server but will fail in Oracle.

Below is the Oracle alternative.

UPDATE 

     (SELECT grade 

             FROM students s

             INNER JOIN students_marks sm ON sm.student_id = s.student_id

             WHERE sm.total_marks>80) t 

SET t.grade='A';

Below is the block diagram for the Oracle query

Find when a DB Object was created in ORACLE

I came across a requirement where I need to find when a table on the schema was modified. I am posting the solution here so as my other fellow programmers can get the idea.

SELECT * FROM  all_objects
WHERE  owner = 'object_owner'
AND object_name = 'object_name'

The column "CREATED" tells you when the object was created. The column "LAST_DDL_TIME" tells you when the last DDL was performed against the object.

Example:

SELECT created
FROM all_objects
WHERE object_name = 'my_table'
AND owner = 'sysdba'
AND object_type = 'TABLE'

It will tell you when a table was created.

The odds are good, but the goods are odd. -S