Hi Andrea,
by reading out pg_constraint [1]
if a UNIQUE constraint is defined the uniqueness is guaranteed by the
db, no need for QGIS to also check it.
Bernhard
[1]
http://www.postgresql.org/docs/9.4/interactive/catalog-pg-constraint.html
Am 04.09.2015 um 08:42 schrieb Andrea Peri:
Ho,
How do qgis to analyze the table to retrieve the unique?
A loop on every record or a SQL to count distinct ?
A.
Il 04/set/2015 08:01, "Bernhard Ströbl" <[email protected]
<mailto:[email protected]>> ha scritto:
Am 03.09.2015 um 23:41 schrieb Sandro Santilli:
On Wed, Sep 02, 2015 at 08:48:34AM +0200, Bernhard Ströbl wrote:
Am 01.09.2015 um 17:49 schrieb Matthias Kuhn:
2. If there are tables without a PK open a second modal
dialog with an
explanation of the problem and offer to select a pk from
a combobox.
I hope you mean "relation" not table, a table should always
have a
PK.
It's not mandatory for a table to have a PK.
I guess by "tables without a PK" he means table for which no PRIMARY
KEY constraint is explicitly defined (should an UNIQUE key be
considered equally valid?).
It is not mandatory, of course, that's why I wrote "should", but
IMHO it is very bad database design to not define one.
There might be several UNIQUE constraints on one table but there can
be only one PK constraint. So in case of only a UINIQUE constraint
the table would be handled as any other without PK constraint (or
QGIS needs to analyse how many fields have a UNIQUE constraint).
Bernhard
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