Обсуждение: "Pretend" update
With "make" I can do "make -n" and it just tells me what it would do but doesn't actually do anything. How could I do that with SQL? I want to write a really complicated (for me) SQL UPDATE statement. I'm sure I won't get it right the first time. Is therean easy way to not really make the changes? I've thought about starting a transaction and then roll it back. That would undo the changes. But I won't be able to tellwhat the changes were. Thank you for your time, Perry
Вложения
On 10/01/2013 10:16 AM, Perry Smith wrote: > With "make" I can do "make -n" and it just tells me what it would do but doesn't actually do anything. > > How could I do that with SQL? > > I want to write a really complicated (for me) SQL UPDATE statement. I'm sure I won't get it right the first time. Isthere an easy way to not really make the changes? > > I've thought about starting a transaction and then roll it back. That would undo the changes. But I won't be able totell what the changes were. Assuming you are not doing this in a function, you can. Do UPDATE, then SELECT to see your changes or not and then ROLLBACK. > > Thank you for your time, > Perry > -- Adrian Klaver adrian.klaver@gmail.com
On Oct 1, 2013, at 12:23 PM, Adrian Klaver <adrian.klaver@gmail.com> wrote: > On 10/01/2013 10:16 AM, Perry Smith wrote: >> With "make" I can do "make -n" and it just tells me what it would do but doesn't actually do anything. >> >> How could I do that with SQL? >> >> I want to write a really complicated (for me) SQL UPDATE statement. I'm sure I won't get it right the first time. Isthere an easy way to not really make the changes? >> >> I've thought about starting a transaction and then roll it back. That would undo the changes. But I won't be able totell what the changes were. > > Assuming you are not doing this in a function, you can. Do UPDATE, then SELECT to see your changes or not and then ROLLBACK. Ah... yes. I forgot you can see the changes within the same transaction. Dohhh... Thank you very much Perry
Вложения
2013/10/1 Perry Smith <pedzsan@gmail.com>
It is possible to use RETURNING clause of the UPDATE statement and avoid SELECT.
On Oct 1, 2013, at 12:23 PM, Adrian Klaver <adrian.klaver@gmail.com> wrote:
> Assuming you are not doing this in a function, you can. Do UPDATE, then SELECT to see your changes or not and then ROLLBACK.
Ah... yes. I forgot you can see the changes within the same transaction. Dohhh...
And yes, it is necessary to do this within a transaction and roll it back after.
--
Victor Y. Yegorov
Victor Y. Yegorov