In a distributed environment how an alias identifies a table

JashBr · New User Joined: 15 Feb 2007 Posts: 2 Location: Chennai

What does it mean that alias doesnt use location qualifier of a table ?
An alias is created even if the table doesnt exist. But how the table structure gets updated ?
In a distributed environment how an alias identifies a table ?

Thanks,
Jash

JashBr · New User Joined: 15 Feb 2007 Posts: 2 Location: Chennai

Hi all,
I'm very much disappointed that none of the viewers replied my post. Atleast send some links from which i could get the answers for above questions.

Thanks,
Jash

expat · Posted: Fri Mar 30, 2007 3:43 pm

vini_srcna · Posted: Fri Mar 30, 2007 8:00 pm

dick scherrer · Posted: Fri Mar 30, 2007 11:33 pm

Hello Jash,

One reason for the lack of response is that your questions were not clear. Another was your statement "An alias is created even if the table doesnt exist." which caused even more confusion.

To get any responses (and especially meaningful ones), care must be given when presenting your question/statment. As i've mentioned several times, while a topic starter's thought/question is completely clear to them, it may not be to those who read it and would want to help.

Good luck

wanderer · Posted: Sat Mar 31, 2007 7:31 am

vini_srcna · Posted: Sat Mar 31, 2007 4:13 pm

wanderer, You made me think.

I know the fact, that an alias would still be there when the table/view on which it is defined is dropped. I was not aware of this concept. Thank you.

I just tried to make sure. Here is the warning message..!
[img]CREATE ALIAS MYALIEAS FOR PILLAR;
---------+---------+---------+---------+---------+---------+---------+---------+
DSNT404I SQLCODE = 403, WARNING: THE LOCAL OBJECT REFERENCED BY THE CREATE
ALIAS STATEMENT DOES NOT EXIST
DSNT418I SQLSTATE = 01522 SQLSTATE RETURN CODE
DSNT415I SQLERRP = DSNXICAL SQL PROCEDURE DETECTING ERROR
DSNT416I SQLERRD = 25 0 0 -1 0 0 SQL DIAGNOSTIC INFORMATION
DSNT416I SQLERRD = X'00000019' X'00000000' X'00000000' X'FFFFFFFF'
X'00000000' X'00000000' SQL DIAGNOSTIC INFORMATION
---------+---------+---------+---------+---------+---------+---------+---------[/img]

Sorry for wrong information and thank you for correcting me. I always love to correct my mistakes

wanderer · Posted: Sat Mar 31, 2007 11:55 pm

I am glad I helped. Cheers

Jash_br · New User Joined: 30 Mar 2007 Posts: 5 Location: Chennai

Wanderer,
So alias can be created even if the table doesn't exist. But how does the alias is updated as soon as we create the table.

wanderer · Posted: Tue Apr 03, 2007 2:16 pm

Jash,

I don't think there is any updation happens and there is no need for such a thing as far as I understand. Why do you think alias needs to be updated when table is created?

vini_srcna · Posted: Tue Apr 03, 2007 2:20 pm

Jash_br · New User Joined: 30 Mar 2007 Posts: 5 Location: Chennai

Hi,
I created an alias for a table which does not exist. I checked that the structure of the alias is empty. Then I created the table. Now again checked the structure of the alias. It got updated with the mentioned table's structure. So how does it happened.

Thanks for your replies

dick scherrer · Posted: Tue Apr 03, 2007 7:20 pm

Hello,

Let's use an anology.

Let's say there is a new housing project under construction (one of the streets is Maple St). Each lot also has a "tract id". All of the new addresses are known before construction begins. There is a reference to 1234 Maple St, but no house or people are there yet. This is like your alias for the table not yet created.

Now the house is built, but not occupied. This is like having a table definition only. Lastly, someone moves into the new house. This is like having data in the new table. You can see who they are, their ages, etc.

Without knowing all of the details and without knowing the tract id, the 123 Maple St address alias is used beacuse it is easier to work with (for many). Much like we would use an alias.

wanderer · Posted: Wed Apr 04, 2007 12:55 am

Jash_br · New User Joined: 30 Mar 2007 Posts: 5 Location: Chennai

Yes Wanderer I just meant DESC of the alias

wanderer · Posted: Wed Apr 04, 2007 1:03 pm

Is this DESC somekind of command you use in some third party tool?

Anyway, it doesn't matter. The whole Alias thing doesn't get updated anywhere if you create the associated table afterwards. Everytime you mention the Alias name, DB2 replaces it with the underlying table name if present based on your Alias definition, before processing your statements further. Hope that explains.

Jash_br · New User Joined: 30 Mar 2007 Posts: 5 Location: Chennai

Got it

Hope thats why Alias is called "Forward pointer" !

Thanks a lot !!!
Jash