Non negative integer column

[Avishay Balderman]

Hi

I would like to create a table with an integer column.

This column value must be >= 0.

How can I enforce it using table defintion?

i have looked here and it looks fine.

http://docs.sqlalchemy.org/en/rel_0_8/core/schema.html?highlight=checkconstraint#sqlalchemy.schema.CheckConstraint

Will it work against any DB?

My backing DB is MySQL.

Thanks

Avishay

[Rory Hart]

from sqlalchemy.dialects.mysql import INTEGER as Integer 
my_int = Column(Integer(unsigned=True))

from: http://blog.luhn.com/post/20919696026/unsigned-integers-with-sqlalchemy-and-mysql

Keep in mind, as Theron notes on his blog post, that this is MySQL specific so you won't have compatibility with other DBs.

Avishay

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[Michael Bayer]

have you considered just using an UNSIGNED INT ?  MySQL offers support for such types.

The CHECK constraint is a good way to go as well, but unfortunately I believe MySQL does not actually enforce CHECK constraints (funny, huh?) .  Here's an SO question regarding that issue: http://stackoverflow.com/questions/5807231/mysql-check-constraint-alternative  .

[Avishay Balderman]

Hi

I am looking for a portable solution - A solution that will work when I switch from DB A to DB B.

so I do not want to include any MySQL specific code.

CheckConstraint looks promising.. but you mentioned it is not supported by MySQL.

Any other ideas?

Thanks

Avishay

[Avishay Balderman]

How about using UserDefinedType  http://docs.sqlalchemy.org/en/rel_0_8/core/types.html#sqlalchemy.types.UserDefinedType and declare a type 'NonNegativeInteger'.

Will it be enough to protect the table from negative integers?

[Michael Bayer]

Oh.  Well a python side rule is very different from a server side rule, but if app side is all you need then sure you have a lot of options there.   Use a TypeDecorator, check the docs there are many examples.

Sent from my iPhone

[Charlie Clark]

Am 10.06.2013, 15:46 Uhr, schrieb Michael Bayer <mik...@zzzcomputing.com>:

> Oh. Well a python side rule is very different from a server side rule,
> but if app side is all you need then sure you have a lot of options
> there. Use a TypeDecorator, check the docs there are many examples.

FWIW David Mertz has just written an interesting checker for Python 3

http://code.activestate.com/recipes/578528-type-checking-using-python-3x-annotations/

Charlie
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[Avishay Balderman]

I prefer to have a server side solution... but cant find a generic one.