database-schema

If I have a table in Postgresql: create table Education ( id integer references Profiles(id), finished YearValue not null, started YearValue, qualification text, schoolName text, studiedAt integer references Organizations(id), primary key (id) ); I need to make a constraint so that either schoolName or studiedAt needs to not be null (one of them has to have information in it). How do I do this? You can use a check constraint e.g. constraint chk_education check (schoolName is not null or studiedAt is not null) From the manual: A check constraint is the most generic constraint type. It allows

I have a column with a uniqueidentifier that can potentially reference one of four different tables. I have seen this done in two ways, but both seem like bad practice. First, I've seen a single ObjectID column without explicitly declaring it as a foreign key to a specific table. Then you can just shove any uniqueidentifier you want in it. This means you could potentially insert IDs from tables that are not part of the 4 tables I wanted. Second, because the data can come from four different tables, I've also seen people make 4 different foreign keys. And in doing so, the system relies on ONE

It seems that org.hibernate.cfg.Configuration object can be used to perform validation programmatically, by calling the validateSchema method. However, this method needs dialect and databaseMetadata objects. I am using Spring and I can get a hold of AnnotationSessionFactoryBean object from spring context. So far I have the following code: AnnotationSessionFactoryBean factory = null; factory = (AnnotationSessionFactoryBean) context.getBean("AnnotationSessionFactory"); Configuration configuration = factory.getConfiguration(); //the following line does not work, ConnectionHelper hierarchy is not

I am just learning how to implement the Nested Set Model but still have confusion with a certain aspect of it involving items that may be part of multiple categories. Given the example below that was pulled from HERE and mirrors many other examples I have come across... How do you avoid duplication in the DB when you add Apples since they are multi-colored (i.e. Red, Yellow, Green)? Lachezar Balev You do not avoid duplications and the apple (or a reference to the apple) will be placed twice in your tree otherwise it won't be a tree but rather a graph. Your question is equally applicable if you

Since I wanted to drop some tables and somebody suggested the below and I did it: postgres=# drop schema public cascade; DROP SCHEMA postgres=# create schema public; CREATE SCHEMA Then I got problem when creating a new database, such as: postgres=# create database test; CREATE DATABASE postgres=# \c test You are now connected to database "test" as user "postgres". test=# create table hi(id int primary key); *ERROR: no schema has been selected to create in* You can see I got error ERROR: no schema has been selected to create in* How can I restore the public schema? I suggest people never do

I want to be able to create schedules that can be executed based on a fixed date, repeated daily, repeated on a particular day of the week, repeated on a particular month of the year, repeated on a particular date every year, and repeated at a particular time of the day. Please how do i go about building the database tables for this problem? Edit #1 Basically, i'm writing an application that allows users to schedule pre-configured greetings to be sent at various pre-configured times. I know i need a table that stores information about a schedule (ex. Christmas, Marketing One, ... | and when

How can I set a unique constraints on two columns? class MyModel extends Migration { public function up() { Schema::create('storage_trackers', function(Blueprint $table) { $table->increments('id'); $table->string('mytext'); $table->unsignedInteger('user_id'); $table->engine = 'InnoDB'; $table->unique('mytext', 'user_id'); }); } } MyMode::create(array('mytext' => 'test', 'user_id' => 1); // this fails?? MyMode::create(array('mytext' => 'test', 'user_id' => 2); Collin James The second param is to manually set the name of the unique index. Use an array as the first param to create a unique key