Clear Case concepts

#1 Clear Case merge

Merge on clear case Diff Merge tools might look confusing at times. Here are 2 scenarios of merging on Diff Merge.

Rebase:

1st window is the base window which contains the version of the file from which the change was made. The changes, made by other and delivered to integration stream, are shown on the 2nd window. And the 3rd window shows the Development stream to which you'd rebase.

Deliver:

1st window is the base window which contains the version of the file from where you've started work on the file and made necessary changes. 2dn window shows the changes now you've in your development stream. And the 3rd window shows Integration stream to which you're going to deliver your changes.

Resources:

http://clearcase.weintraubworld.net/ - not-so-official clear case website
http://clearcase.weintraubworld.net/cc.branch.html#real - Branching theory of clear case
http://clearcase.weintraubworld.net/cc.branch2.html - Branching strategy

Useful ClearCase commands

Frequently used cleartool commands:

List out the checked out files
cleartool> lsco

Check in a file
cleartool>ci [-nc] filename

Check out a file
cleartool>co filename

Undo a check out
cleartool>unco filename

Add a file to source control
cleartool>mkelem filename


Resources:

http://techpubs.sgi.com/library/tpl/cgi-bin/getdoc.cgi?cmd=getdoc&coll=0530&db=man&fname=1%20cleartool - Contains list of commands
http://www.ibm.com/developerworks/rational/library/836.html - cheat sheet

Oracle Table Join

There are mainly 3 types of Joins in Oracle - Cartesian Join or Cross Join, Inner Join and Outer Join

Cartesian Join: This join returns the cartesian product of two tables i.e. match all the rows of one table to every rows of another table

Inner Join: when two tables are joined to retrieve all the matched rows in two tables

Outer Join: There are different flavors of Outer Joins: Full Outer Join, Left Outer Join, Right Outer Join. They're described with exmple illustration below:

Full outer join
Takes all matched rows from both table and then all the unmatched rows from left as well as right table

select one.id as one_id, one.name as one_name , two.id as two_id, two.address as two_address
from one full outer join two on one.id = two.id


Left outer join
Takes all the matches as well as the unmatched rows from left table (i.e. table one)

Deprecated syntax:
select one.id as one_id, one.name as one_name , two.id as two_id, two.address as two_address
from one, two
where one.id = two.id(+)

Suggested syntax:
from table1 left outer join table2
on table1.col = table2.col



Right outer join
Takes all the rows that have match as well as the all the left over rows from the right table (i.e. table two)

Deprecated syntax
select one.id as one_id, one.name as one_name , two.id as two_id, two.address as two_address
from one, two
where one.id(+) = two.id

Suggested syntax
select one.id as one_id, one.name as one_name , two.id as two_id, two.address as two_address
from one right outer join two on one.id = two.id



There is another flavors of Join which is known as Self Join where both the tables are actually the same table but used with alias. All the 3 kinds of Joins mentioned above can be used for the self join

Resources

http://www.praetoriate.com/oracle_tips_outer_joins.htm - Donald K. Burleson on Joins. He writes very straight & simple.
http://www.sqlteam.com/article/additional-criteria-in-the-join-clause - Filtering the join