Contents
Can a primary key column have duplicate values?
A primary key is a column of table which uniquely identifies each tuple (row) in that table. Only one primary key is allowed to use in a table. The primary key does not accept the any duplicate and NULL values.
How do you make sure there are no duplicate values in a column database?
The go to solution for removing duplicate rows from your result sets is to include the distinct keyword in your select statement. It tells the query engine to remove duplicates to produce a result set in which every row is unique. The group by clause can also be used to remove duplicates.
Can a primary key be duplicated in another column?
I must stress however that, although possible, this is usually bad design! Primary keys are unique, so if you want to have duplicate data in a certain column, that same column can’t be the primary kay of that table. Thanks for contributing an answer to Stack Overflow!
Is it possible to insert duplicate records in SQL Server?
No, it is not possible in SQL Server to insert records that have duplicate values in the Primary Key. I would also add that is not possible in any of the relational database engines by defenition.
Can a identity key be used as a primary key?
Primary key, one can define on specific column of the table. Identity key can be used as primary key. But you can have identity column as well primary key on same table. Primary key is one and only for the table.So if you are treating identity as primary key, then you will have no further table column as primary key.
When is it desired to declare a primary key?
When it was desired to declare a primary key, it was necessary to clear up the data error first, in order to be able to use the most logical column as a primary key. So my advice is to see whether all the data in your table conforms to the business rules as well as checking to see if the business rules imply using this column as a primary key.