Re: [Pypgsql-users] problems with returned data sets

[Gerhard H. <gh...@gh...>]

On Thu, Nov 04, 2004 at 05:55:11PM +1000, Timothy Smith wrote:
> ok i get that but it is still giving me problems. the error i get is
> libpq.OperationalError: ERROR:  column "groupmembership" does not exist
>=20
> but it DOES exisit? there must be some syntax error i'm making. pyPgSQL=
=20
> has bearly any real documentation so these errors are easy to make....
>=20
> #Get groups which this user belongs to
>    cur.execute("SELECT UserGroup FROM UserMenuInfo WHERE UserName =3D=20
> UserName")
>    Groups =3D cur.fetchone()
>    GroupMembership =3D Groups[0]
>=20
> *snip* =20
>  =20
>    #Get menu items which this user has access to
>    cur.execute("SELECT MenuName FROM MenuItems WHERE UserGroup =3D=20
> GroupMembership")

"WHERE UserGroup =3D GroupMembership" means you join two columns in SQL. To
compare a column with a string, you use something like "WHERE UserGroup =3D
'Group1'", to compare it with a number "WHERE UserGroup =3D 42'.

Now, it appears you want to parametrize your query. That's what the additio=
nal
parameter of .execute() is for: to give it a sequence of query parameters:

cur.execute("SELECT Menuname FROM MenuItems WHERE UserGroup =3D %s", (Group=
Membership,))

The placeholder in pyPgSQL is always %s.

-- Gerhard
--=20
A: Because it messes up the order in which people normally read text.
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