Can any kind soul clarify my doubts with a simple example below and identify the superkey, candidate key and primary key? I know there are a lot of posts and websites out there explaining the differences between them. But it looks like all are generic definitions. Example: So from the above example, I can know StudentNumber is a primary key.
Tag: primary-key
Foreign Key Used in Composite Primary Key
Is it possible to use a composite foreign key as a piece of a table’s composite primary key? For instance, let’s say I have two tables: … and then in a second table, I would like to reference the foreign key in the second table’s primary key: Is there any way that I can do that? Yes, it might be
Some sort of “different auto-increment indexes” per a primary key values
I have got a table which has an id (primary key with auto increment), uid (key refering to users id for example) and something else which for my question won’t matter. I want to make, lets call it, different auto-increment keys on id for each uid entry. So, I will add an entry with uid 10, and the id field
Finding a Primary Key Constraint on the fly in SQL Server 2005
I have the following SQL: Since I have multiple environments, that PK_PS_userVariables constraint name is different on my different databases. How do I write a script that gets that name then adds it into my script? Answer While the typical best practice is to always explicitly name your constraints, you can get them dynamically from the catalog views:
Indexes and multi column primary keys
In a MySQL database I have a table with the following primary key In my application I will also frequently be selecting on item by itself and less frequently on only invoice. I’m assuming I would benefit from indexes on these columns. MySQL does not complain when I define the following: But I don’t see any evidence (using DESCRIBE —
When should I use primary key or index?
When should I use a primary key or an index? What are their differences and which is the best?
Determine a table’s primary key using TSQL
I’d like to determine the primary key of a table using TSQL (stored procedure or system table is fine). Is there such a mechanism in SQL Server (2005 or 2008)?
Moving from ints to GUIDs as primary keys
I use several referenced tables with integer primary keys. Now I want to change ints to GUIDs leaving all references intact. What is the easiest way to do it? Thank you! Addition I do understand …