DAL how to increment column value

[Rob Paire]

Hello all,

I am wondering if it's possible to use DAL update method to increment the value of table column H_REVNO in one line of code, and one trip to the database?

I tried this query, and a couple of similar variations, but could not get it to work.

db(db.KICKER.id == request.vars.kicker_id).update(H_REVNO=H_REVNO+1)

Here is what I am using for now

db.executesql("update KICKER set H_REVNO = H_REVNO + 1 where ID = "+ str(request.vars.kicker_id))  which of course works. 

Thank you all!

[黄祥]

perhaps can learn from book :
http://web2py.com/books/default/chapter/29/11/jquery-and-ajax#Voting-and-rating

best regards,

stifan

[Carlos Correia]

Às 18:20 de 20/05/21, Rob Paire escreveu:

Hi,

Using DAL you have to read the record first in other to get the value to be incremented. But, if there are many users it might lead to corrupted values due to concurrency.

As far as I know, the latest is the only sane approach to solve your problem.

Carlos Correia
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[Rob Paire]

Hi All

Thank you for the helpful comments!  I am fine leaving the SQL Execute statement in place, but thought the question was worth asking.

-Rob

[valq...@gmail.com]

db(...).update(some_field = db.some_table.some_field_or_another_field + 1)

- should work ( it is a single db-query)

вторник, 25 мая 2021 г. в 19:59:34 UTC+3, Rob Paire:

[valq...@gmail.com]

http://www.web2py.com/books/default/chapter/29/06/the-database-abstraction-layer#Expressions

вторник, 25 мая 2021 г. в 22:36:47 UTC+3, valq...@gmail.com:

[Rob Paire]

Ah ha!!! Excellent - that looks so much better now!  I appreciate your help

-Rob