AUTO_INCREMENT in MySQL and Sequence in Oracle SQL

In Oracle SQL, there is noAUTO_INCREMENT keyword like in MySQL. This is because Oracle handles auto-increment functionality differentlyusing sequences and optionally triggers. While MySQL has the AUTO_INCREMENT keyword to automatically generate unique numeric values, Oracle relies on the flexibility of sequences to achieve the same outcome.

Why Oracle Doesn't Use AUTO_INCREMENT

Oracle focuses on database objects like sequences to provide more granular control over value generation.

Using sequences, you can:

• Set custom starting values.
• Define the increment step.
• Manage caching or cycling of values.
• This makes sequences more versatile than the fixed AUTO_INCREMENT approach.

How Oracle Implements Auto-Increment Without AUTO_INCREMENT

Instead of using an AUTO_INCREMENT keyword, Oracle uses the following steps:

1. Create a Sequence: Defines how unique values are generated.

CREATESEQUENCEmy_table_seqSTARTWITH1INCREMENTBY1NOCYCLE;

2. Use a Trigger (Optional): Automates the assignment of sequence values to a column.

CREATEORREPLACETRIGGERmy_table_triggerBEFOREINSERTONmy_tableFOREACHROWBEGIN:NEW.id:=my_table_seq.NEXTVAL;END;/

3. Direct Sequence Usage: Insert rows by explicitly calling the sequence.

INSERTINTOmy_table(id,column1)VALUES(my_table_seq.NEXTVAL,'value1');

Key Takeaway

• The AUTO_INCREMENT keyword does not exist in Oracle SQL. Instead:
• Use sequences to generate unique identifiers.
• Optionally, automate this with triggers for convenience.

This approach provides flexibility while achieving functionality similar to AUTO_INCREMENT.