Identity column vs Sequence in SQL
Identity Column
what is the identity column?
The identity column is a numeric column in the table, enabling auto integer values to be generated every time the row is inserted, it is mainly filled with integer values but it can be filled with other
datatypes like bigint,smallint, tinyint, or decimal as long as the scale is 0.
why use the identity column?
because it saves you time adding repeated numbers in famous columns like id
How can we apply the identity column?
- first, select the database from MSSMS
- second, choose the database and column where you want to apply identity
- third check the identity specification
Sequence
What is the Sequence?
A sequence is an object in SQL Server (Transact-SQL) that is used to generate a number sequence.
why use the identity Sequence?
because it is Useful for generating primary keys, surrogate keys, or any other scenario where unique values are required.
How can we apply Sequence?
Sequence_Name − This specifies the name of the sequence.
Initial_Value − This specifies the starting value from where the sequence should start.
Increment_Value − This specifies the value by which the sequence will increment by itself. This can be valued positively or negatively.
Minimum_Value − This specifies the minimum value of the sequence.
Maximum_Value − This specifies the maximum value of the sequence.
Cycle − When the sequence reaches its maximum value, it starts again from the beginning.
Nocycle − An exception will be thrown if the sequence exceeds the Maximum_Value.
Now let's make a simple table to compare between identity column and the sequence
At the end
Identity columns are straightforward and best for single-table unique identifiers, while sequences offer more flexibility and are ideal for more complex or shared numbering needs.
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