unique-constraint

问题 I have an entity which has @OneToMany private ownership of a collection of another entities. That other entity has some unique constraints over different set of columns. The problem arises when I want to update the main entity (together with changed child entities). EclipseLink does insert before delete, so sometimes, an insertion violates the constraint and throws an exception. Is there a way to force the deletion of child entities before inserting their updated counterparts? 回答1: I know, I

问题 I have a SQLAlchemy model on which I want to run validation. Part of the validation is to ensure a UniqueConstraint exists on a (few) column(s). I know what the columns are. Is there a good way to do this with SQLAlchemy? The underlying database I am using is MySQL. 回答1: You could use SQLalchemy reflection API. In order to get the unique constraints, issue a get_unique_constraints. Primary keys are unique, so you must issue a get_pk_constraint too. table created with: CREATE TABLE user ( id

问题 I have a SQLAlchemy model on which I want to run validation. Part of the validation is to ensure a UniqueConstraint exists on a (few) column(s). I know what the columns are. Is there a good way to do this with SQLAlchemy? The underlying database I am using is MySQL. 回答1: You could use SQLalchemy reflection API. In order to get the unique constraints, issue a get_unique_constraints. Primary keys are unique, so you must issue a get_pk_constraint too. table created with: CREATE TABLE user ( id

问题 I have a problem using Djangos Default user from django.contrib.auth.models but trying to use it with my custom User model, using from django.contrib.auth.models import AbstractUser . So here is my User model: from django.db import models from django.contrib.auth.models import AbstractUser, UserManager as AbstractUserManager # from django.conf import settings from django_countries.fields import CountryField # https://github.com/SmileyChris/django-countries from django.db.models.signals import

问题 I have a problem using Djangos Default user from django.contrib.auth.models but trying to use it with my custom User model, using from django.contrib.auth.models import AbstractUser . So here is my User model: from django.db import models from django.contrib.auth.models import AbstractUser, UserManager as AbstractUserManager # from django.conf import settings from django_countries.fields import CountryField # https://github.com/SmileyChris/django-countries from django.db.models.signals import

问题 I have this table: XPTO_TABLE (id, obj_x, date_x, type_x, status_x) I wanna create a unique constraint that applies to the fields (obj_x, date_x, type_x) only when status_x <> 5 . I have tried to create this one but Oracle says: line 1: ORA-00907: missing right parenthesis CREATE UNIQUE INDEX UN_OBJ_DT_TYPE_STATUS ON XPTO_TABLE( (CASE WHEN STATUS_X <> 5 THEN (OBJ_X, TO_CHAR (DATE_X, 'dd/MM/yyyy'), TYPE_X) ELSE NULL END)); What's the correct syntax ? 回答1: @jamesfrj: it looks like you are

问题 I am building a small app and at this point I am creating the database schema. I use PostgreSQL with Sequel and I have the two migrations: Sequel.migration do change do Sequel::Model.db.run 'CREATE EXTENSION IF NOT EXISTS "uuid-ossp"' create_table :user do String :id, :type => :uuid, :primary_key => true, :default => Sequel.function(:uuid_generate_v4) DateTime :created_at DateTime :updated_at index :id, :unique => true end end end Sequel.migration do change do Sequel::Model.db.run 'CREATE

问题 In my Django project the in one of the model I need to use two UniqueConstraint instances. But when I add that and do the migration after running makemigrations it gives an error in the terminal. Model class: class MyDays(models.Model): class Meta: verbose_name = "My Day" verbose_name_plural = "My Days" constraints = [ models.UniqueConstraint(fields=['userid', 'date', 'from'], condition=Q(status=1), name='user_date_from_a'), models.UniqueConstraint(fields=['userid', 'date', 'to'], condition=Q

问题 I'm trying to check if the room that is going to be inserted in the system is already rented at that date or not. I've though about counting the rows that match both the room number and the date, and then rolling back the transaction. But I'm getting the following error, even though I have changed the code to raise user-defined exceptions: ERROR: cannot begin/end transactions in PL/pgSQL HINT: Use a BEGIN block with an EXCEPTION clause instead. CONTEXT: PL/pgSQL function "checkRoom"() line 17

问题 I have a table with a column that must have UNIQUE values (but it could be also a multiple-column UNIQUE index, the problem is the same). In my PHP script I have to insert a row in that table. I'm searching for a way, not MySQL-specific, to exit the PHP script if there's a problem, and the problem is not a violation of a UNIQUE constraint. To make things more easy I don't want to use a SELECT query before :D Currently I'm doing something like this: try { $stmt = $dbh->prepare($someinsertquery