unique-index

I have a SAMPLE_TABLE with a column BIZ_ID which should be unique when the column active is not equal to 0. On an oracle database the index looks like this: CREATE UNIQUE INDEX ACTIVE_ONLY_IDX ON SAMPLE_TABLE (CASE "ACTIVE" WHEN 0 THEN NULL ELSE "BIZ_ID" END ); How would this unique index look like on a h2 database? In H2, you could use a computed column that has a unique index: create table test( biz_id int, active int, biz_id_active int as (case active when 0 then null else biz_id end) unique ); --works insert into test(biz_id, active) values(1, 0); insert into test(biz_id, active) values(1,

I asked a similar question here at Uniqueness validation in database when validation has a condition but my requirements have changed, hence this question. Using uniqueness validations in Rails is not safe when there are multiple processes unless the constraint is also enforced on the database (in my case a PostgreSQL database so see http://robots.thoughtbot.com/the-perils-of-uniqueness-validations ). In my case, the uniqueness validation is conditional: it should only be enforced if another attribute on another model becomes true. So I have class Parent < ActiveRecord::Base # attribute is

Often when I define a View in Navicat I receive the following message: xxx does not have a primary key. Updates to this table will be done using the following pseudo statement: UPDATE xxx SET ModifiedFieldsAndValues WHERE AllFieldsAndOldValues LIMIT 1 Obviously I only use my Views for viewing data, not updating . But this did make me curious: Is there a way to define a "primary key" or "unique index" on a View? its implied that the view uses the indices and primary keys of its base table. You can change the semantics of how insert and updates occur when using them via views by playing with the

I've got a MySQL table that stores urls as unique keys. I'm starting to get collisions on my keys because it seems the keys themselves are only the first 64 bytes (or characters if you prefer, its a latin-1 collated) of any url. So if a url is over 64 characters and I've already got a similar url it throws an error. For example: SELECT l.link_id FROM mydb.links l WHERE url = 'http://etonline.com/tv/108475_Charlie_Sheen_The_People_Have_Elected_Me_as_Their_Leader/index.html' Throws this error: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'http://etonline.com/tv/108475

Using uniqueness validations in Rails is not safe when there are multiple processes unless the constraint is also enforced on the database (in my case a PostgreSQL database, so see this blog post ). In my case, the uniqueness validation is conditional: it should only be enforced if another attribute in the model becomes true. So I have class Model < ActiveRecord::Base validates_uniqueness_of :text, if: :is_published? def is_published? self.is_published end end So the model has two attributes: is_published (a boolean) and text (a text attribute). text should be unique across all models of type

On one of my PostgreSQL tables, I have a set of two fields that will be defined as being unique in the table, but will also both be used together when selecting data. Given this, do I only need to define a UNIQUE INDEX, or should I specify an INDEX in addition to the UNIQUE INDEX? This? CREATE UNIQUE INDEX mytable_col1_col2_idx ON mytable (col1, col2); Or this? CREATE UNIQUE INDEX mytable_col1_col2_uidx ON mytable (col1, col2); CREATE INDEX mytable_col1_col2_idx ON mytable (col1, col2); Mark Byers If you have a UNIQUE INDEX then you don't also need the INDEX - it would be redundant. A UNIQUE

I have the following in my migration file def self.up create_table :payment_agreements do |t| t.boolean :automatic, :default => true, :null => false t.string :payment_trigger_on_order t.references :supplier t.references :seller t.references :product t.timestamps end end I want to ensure that if a product_id is specified it is unique but I also want to allow null so I have the following in my model: validates :product_id, :uniqueness => true, :allow_nil => true Works great but I should then add an index to the migration file add_index :payment_agreements, :product_id, :unique => true Obviously