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Can composite primary key be duplicated?
It is allowing duplicates. The only possibility which is not allowed is the duplicates of the composite keys(studentID,classID) as like “C. Champagne” said.
Why can’t you enter duplicate values in primary key fields?
No. The point of a primary key is to identify an attribute or a combination of attributes that uniquely identify the row. If any two or more records had the same primary key, it would be impossible to distinguish those rows from each other. If a primary key is composite, then a single column could have duplicates.
Is primary key composite key?
Now a composite key is also a primary key, but the difference is that it is made by the combination of more than one column to identify the particular row in the table.
Does unique key allow duplicate values?
A unique key is a set of one or more than one fields/columns of a table that uniquely identify a record in a database table. You can say that it is little like primary key but it can accept only one null value and it cannot have duplicate values.
Is it possible to ignore duplicate primary key in SQL?
In other words, you can’t ignore a primary key. It is defined as unique and not-null. If you want the table to have duplicates, then that is not the primary key. Thanks for contributing an answer to Stack Overflow!
Can a primary key be duplicated in hp COBOL?
In HP COBOL compatibility mode, duplicate primary key values are allowed if the indexed file system supports them and the WITH DUPLICATES phrase is specified in the File-Control paragraph. Vision and KSAM support duplicate primary key values.
Is it possible to have two primary keys?
You cannot have 2 Primary Keys. You can have multiple Unique Keys if needed, which should help you in your case. Make sure to go back to your table creation and double check which column is your Primary Key and work from there. Share Improve this answer Follow answered Apr 16 ’16 at 23:32 smul86smul86
What’s the meaning of ” with no duplicates “?
The syntax is: The phrase “WITH NO DUPLICATES” is commentary because, by default, duplicate values are not allowed for the primary key. The phrase “WITH DUPLICATES” indicates that duplicate primary key values are allowed.