What is the difference between primary and unique index?
- What is difference between primary and unique?
- What are the main differences between primary key and unique key?
- What does unique index mean?
- What is difference between index and primary key?
What is difference between primary and unique?
Both Primary key and Unique Key are used to uniquely define of a row in a table. Primary Key creates a clustered index of the column whereas a Unique creates an unclustered index of the column . A Primary Key doesn't allow NULL value , however a Unique Key does allow one NULL value .
What are the main differences between primary key and unique key?
The primary key is accepted as a unique or sole identifier for every record in the table. In the case of a primary key, we cannot save NULL values. In the case of a unique key, we can save a null value, however, only one NULL value is supported.
What does unique index mean?
Unique indexes are indexes that help maintain data integrity by ensuring that no rows of data in a table have identical key values. When you create a unique index for an existing table with data, values in the columns or expressions that comprise the index key are checked for uniqueness.
What is difference between index and primary key?
The primary key are the column(s) that serves to identify the rows. An index is a physical concept and serves as a means to locate rows faster, but is not intended to define rules for the table.
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