MAXVALUE FAQS

 1. What is MAXVALUE in Oracle sequences?

• MAXVALUE specifies the maximum value that a sequence can generate. Once the sequence reaches this value, it will either stop generating values (if CYCLE is not used) or restart at a defined value (if CYCLE is used).

2. Can I create a sequence without specifying MAXVALUE?

• Yes, if you don't specify MAXVALUE, Oracle will automatically set the maximum value to the largest possible number based on the datatype used for the sequence. For example, an ascending sequence will have the largest number as 10^27 - 1.

3. What happens if the sequence reaches its MAXVALUE?

• If the sequence reaches its MAXVALUE, and the sequence is not set to cycle, Oracle will throw an error when you attempt to generate the next sequence number.
• If the sequence is set to cycle (using the CYCLE option), the sequence will restart from the MINVALUE or the START WITH value, depending on whether it is an ascending or descending sequence.

4. Can I change the MAXVALUE for an existing sequence?

• You cannot directly modify the MAXVALUE of an existing sequence. To change the MAXVALUE, you would need to drop and recreate the sequence.

5. What is the default MAXVALUE for an ascending sequence?

• For an ascending sequence, if no MAXVALUE is specified, Oracle will use the largest possible number (10^27 - 1).

6. What is the default MAXVALUE for a descending sequence?

• For a descending sequence, if no MAXVALUE is specified, Oracle will use the smallest possible number (-10^27 + 1).

7. Can I set both MINVALUE and MAXVALUE for a sequence?

• Yes, you can set both MINVALUE and MAXVALUE for a sequence. These values define the lower and upper boundaries within which the sequence can generate numbers. Additionally, you can combine them with the CYCLE option to create a sequence that wraps around after reaching the limits.

8. How does MAXVALUE work with the CYCLE option?

• If a sequence is created with the CYCLE option, once it reaches the MAXVALUE, it will restart from the MINVALUE or the START WITH value. This creates a circular sequence where the values repeat.

9. What happens if the MAXVALUE is lower than the MINVALUE in a sequence?

• For an ascending sequence, the MAXVALUE must be greater than the MINVALUE. Conversely, for a descending sequence, the MAXVALUE must be less than the MINVALUE. Setting these values incorrectly will result in an error when creating the sequence.

10. Can I use MAXVALUE to prevent a sequence from generating excessively large values?

• Yes, by setting a MAXVALUE, you can ensure that the sequence does not generate excessively large values, which can be useful to avoid overflow or to adhere to business rules.

11. How can I ensure a sequence doesn’t exceed a specific number using MAXVALUE?

• Simply set the MAXVALUE to the desired upper limit. For example, if you want a sequence to generate numbers between 1 and 100, you would set MAXVALUE to 100 when creating the sequence.

12. Can I use MAXVALUE with both ascending and descending sequences?

• Yes, MAXVALUE can be used with both ascending and descending sequences. For ascending sequences, the MAXVALUE defines the upper limit, while for descending sequences, it defines the lowest point in the descending range.