| From: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | Michael Moore <michaeljmoore(at)gmail(dot)com> |
| Cc: | postgres list <pgsql-sql(at)postgresql(dot)org> |
| Subject: | Re: NOT NULL CHECK (mycol !='') :good idea? bad idea? |
| Date: | 2016-06-03 18:37:20 |
| Message-ID: | CAKFQuwa1C5EHj2jBL=Jbsx5sWd+EG325yC-VBsoM5Dg=vX5yaQ@mail.gmail.com |
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| Lists: | pgsql-sql |
On Fri, Jun 3, 2016 at 2:16 PM, Michael Moore <michaeljmoore(at)gmail(dot)com>
wrote:
> In Oracle, a NOT NULL constraint on a table column of VARCHAR in essence
> says: "You need to put at least 1 character for a value". There is no such
> thing as a zero-length string in Oracle, it's either NULL or it has some
> characters.
>
> To make Postgres perform an equivalent column edit, I am considering
> defining table columns like ... mycol VARCHAR(20) NOT NULL CHECK (mycol
> !='')
>
> Is there any drawback to this? Is there a better way to do it? Any
> thoughts? how about ....
> mycol VARCHAR(20) NOT NULL CHECK (length(mycol) > 0)
> or even
> mycol VARCHAR(20) CHECK (length(mycol) > 0)
>
>
That seems like the best choice. Equality checks should be faster than
length detection.
Dave
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