Oracle Learning (22) sequence (sequence)

When a sequence is invoked for the first time, it returns a predetermined value, and in each subsequent query call, the sequence produces a value that is obtained by its specified increment.

1. Create sequence

The syntax format is as follows:

Create sequence [schema.] Sequence_name  
[Increment by Incre_value]--each increment, by default, is 1*/  
[start with Start_value]--Initial value */  
[MaxValue Integer | Nomaxvalue]--Maximum value */  
[minvalue integer | nominvalue]-min/  
[cycle | nocycle]-cycle/  
[Cache integer | NOCAC He]--buffer set/  
[order | noorder]--serial number is generated in sequence * *

Sample code:

Create sequence mysequence increment by 2-start with 1;

2, the use of the sequence

After the sequence is created, a value is returned each time the Sequence_name.nextval is invoked.

Sample code:

Select Mysequence.nextval from dual;

2, modify the sequence

The syntax format is as follows:

Alter sequence [schema.] Sequence_name  
[Increment by integer_value]  
[MaxValue integer | nomaxvalue]  
[MinValue integer | Nominvalue]  
[cycle | nocycle]  
[Cache integer | nocache]  
[order | noorder]

Sample code:

Alter sequence mysequence increment by 1 MaxValue 1000;

3. Delete sequence

The syntax format is as follows:

Drop sequence sequence_name;

Sample code:

Drop sequence mysequence;

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