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 kno…
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, i…
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 …
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’…
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 …