primary-key

I have the following tables (Primary key in bold . Foreign key in Italic ) Customer table ID---Name ---Balance--- Account_Name --- Account_Type Account Category table Account_Type ----Balance Customer Detail table Account_Name ---First_Name----Last_Name---Address Can I have two foreign keys in the Customer table and how can I implement this in MySQL? Updated I am developing a web based accounting system for a final project. Account Category Account Type --------------Balance Assets Liabilities Equity Expenses Income Asset Asset_ID -----Asset Name----Balance---- Account Type Receivable

I have table 1 with a primary key user_id and table 2 where user_id is a foreign key. Only 1 record per user_id can exist in table 2, and no record can exist without it. QUESTION: Can user_id in table 2 be both foreign and primary key at the same time, and if yes, is it a good idea, what are pros/cons? Yes, you can do this (and you should, from a database design point of view). However, consider what it means if user_id is the primary key on table 2. You are in effect saying that each row in table 2 corresponds to a user, but you already have a table where each row corresponds to a user: table

I have noticed that setting PK is not obligatory in Realm and simply can be omitted. But in documentation is stated that: Indexes are created automatically for primary key properties. And I'd like to clear up some questions: 1) What is the default value for PK is defined by Realm, if I don't assign it by myself. Is it hash or whatever ? (If I don't set PK and call [MyRealmObject primaryKey] it returns nil ) 2) If this implicit PK is indexed by default ? Should I worry about it, because if it is not indexed, does it mean that it affects the general performance of this Entity (for example

I have heard a few references that pk is not required on fact table. I believe every single table should have a pk. How could a person understand a row in a fact table if there is no pk and 10+ foreign keys. Primary Key is there ... but Enforcing the primary key constraint in database level is not required. If you think about this, technically a unique key or primary key is a key that uniquely defines the characteristics of each row. And it can be composed of more than one attributes of that entity. Now in the case of a Fact table, foreign keys flowing-in from the other dimension tables

Is this the best way to - Get a List of all Primary Keys in a Database - or is there something better? SELECT KCU.TABLE_NAME AS Table_Name, KCU.CONSTRAINT_NAME AS Constraint_Name, KCU.COLUMN_NAME AS COLUMN_NAME FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS TC JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU ON KCU.CONSTRAINT_SCHEMA = TC.CONSTRAINT_SCHEMA AND KCU.CONSTRAINT_NAME = TC.CONSTRAINT_NAME AND KCU.TABLE_SCHEMA = TC.TABLE_SCHEMA AND KCU.TABLE_NAME = TC.TABLE_NAME WHERE TC.CONSTRAINT_TYPE = 'PRIMARY KEY' ORDER BY KCU.TABLE_SCHEMA, KCU.TABLE_NAME, KCU.CONSTRAINT_NAME look on link EXEC sp_pkeys '

HI, Using: SQL Server Database: Northwind I'd like to drop a table primary key, without knowing the PK constraint name.. eg, using the Categories table in the Northwind Sample database, the primary key column is 'CategoryId', and the primary key name is 'PK_Categories' I can drop the primary key while knowing the primary key name: ALTER TABLE categories DROP CONSTRAINT PK_Categories; And I can also get the primary key name for the table by table name: select name from sysobjects where xtype = 'PK' and parent_obj = object_id('categories') However, I cannot put them together to delete a table's

I have users table in my PostgreSQL 9.3.6 database with two columns: id and another_id . The id is a primary key, the another_id is just another integer column with unique constraint. There are other tables that reference users by primary key. Here's the users table description: Table "public.users" Column | Type | Modifiers | Storage | Stats target | Description ----------------------+--------------------------------+----------------------------------------+---------+--------------+------------- id | integer | not null | plain | | another_id | integer | not null | plain | | Indexes: "users