START WITH FAQS

 1. What does the START WITH clause do in an Oracle sequence?

  • The START WITH clause defines the starting value of the sequence. This is the first value generated by the sequence when you call NEXTVAL for the first time.

2. What is the default value for START WITH if it is not specified?

  • If START WITH is not specified:
    • For ascending sequences, the default starting value is 1.
    • For descending sequences, the default starting value is -1.

3. Can I change the START WITH value of an existing sequence?

  • No, once a sequence is created, you cannot modify the START WITH value directly. To change the starting value, you must drop and recreate the sequence with the new START WITH value.

4. Can I specify a negative value for START WITH?

  • Yes, you can specify a negative value for START WITH, especially if you are creating a descending sequence where values will decrease over time.

5. What happens when the sequence reaches the MAXVALUE or MINVALUE?

  • If the sequence is created with the CYCLE option, once it reaches the MAXVALUE (for ascending sequences) or MINVALUE (for descending sequences), it will restart from the START WITH value. If NOCYCLE is used, the sequence will stop generating values once the maximum or minimum value is reached.

6. Can I set START WITH to a value other than 1 or -1?

  • Yes, you can set the START WITH value to any integer, including values greater than 1 or less than -1, depending on the specific use case or business requirements.

7. What is the impact of START WITH on the sequence values?

  • The START WITH value directly determines the first value returned by the sequence. Subsequent values will be determined by the INCREMENT BY value.

8. Can START WITH be used in combination with CYCLE or NOCYCLE?

  • Yes, you can use START WITH with the CYCLE or NOCYCLE options. If CYCLE is specified, the sequence will restart from the START WITH value once the MAXVALUE or MINVALUE is reached. If NOCYCLE is used, the sequence will stop generating values after reaching the limit.

9. What if I set START WITH to a value greater than MAXVALUE or smaller than MINVALUE?

  • If the START WITH value is greater than MAXVALUE (for ascending sequences) or smaller than MINVALUE (for descending sequences), Oracle will raise an error when creating the sequence. The START WITH value must respect the limits set by MINVALUE and MAXVALUE.

10. How do I know the current value of START WITH for a sequence?

  • The current value of the sequence, including the starting value, is not directly retrievable from the sequence itself once it's been created. However, you can use CURRVAL to find the most recent value, or you can query the metadata of the sequence, such as through USER_SEQUENCES.

11. What is the effect of START WITH on the order of sequence numbers?

  • The sequence will always start from the value specified in START WITH. For ascending sequences, values will increase by the specified INCREMENT BY, and for descending sequences, values will decrease by the same amount.

12. Can I use START WITH in a sequence that generates random or non-numeric values?

  • No, START WITH applies only to numeric sequences. If you need random or non-numeric values, you would have to use different methods, such as using DBMS_RANDOM or generating random values manually.

 

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