How to use oracle sequence

Oracle sequences are used to generate unique sequences of numbers, usually used as primary keys or identifiers. Creating a sequence requires specifying the sequence name, starting value, incremental value, maximum value, minimum value, cache size, and loop flags. When using a sequence, use the NEXTVAL keyword to get the next value of the sequence.

How to use Oracle Sequences

Oracle sequence is a database object used to generate a series of unique numbers. It is usually used to assign primary keys or other identifiers to records in a table.

Create a sequence

To create a sequence, use the following syntax:

 <code class="sql">CREATE SEQUENCE sequence_name START WITH start_value INCREMENT BY increment_value MAXVALUE max_value MINVALUE min_value CACHE size CYCLE;</code>

• sequence_name: The name of the sequence.
• start_value: The start value of the sequence.
• increment_value: The value of the sequence that grows each time the sequence is called.
• max_value: The maximum value of the sequence.
• min_value: The minimum value of the sequence.
• CACHE: Specifies the size of the sequence cache in memory.
• CYCLE: Indicates whether the sequence should restart from start_value after max_value is reached.

Use sequence

To use the sequence, use the NEXTVAL keyword. This returns the next value of the sequence:

 <code class="sql">SELECT NEXTVAL('sequence_name');</code>

Example

The following example creates a sequence called my_sequence , starting from 1, incrementing by 1 for each call, with a maximum value of 100,000:

 <code class="sql">CREATE SEQUENCE my_sequence START WITH 1 INCREMENT BY 1 MAXVALUE 100000;</code>

To use this sequence we can run the following query:

 <code class="sql">SELECT NEXTVAL('my_sequence');</code>

This will return the current value of the sequence, i.e. 1. Running the query again will return 2, and so on.

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