Current value of a sequence

Question

Suppose my sequence X_SEQ has a cache size of 20,
then will
SELECT LAST_NUMBER - CACHE_SIZE "Current value of x_seq" FROM USER_SEQUENCES WHERE SEQUENCE_NAME = 'X_SEQ' ;
always give me the current value of this sequences or would there be any unforeseen exceptions ?
Thanks

Answer 1

Check this example.
SQL> create sequence myseq
  2  start with 1 increment by 1
  3  nocycle nocache;
Sequence created.
SQL>  SELECT LAST_NUMBER - INCREMENT_BY "Current value of x_seq" FROM USER_SEQUENCES
  2  WHERE SEQUENCE_NAME = 'MYSEQ';
Current value of x_seq
                     0
SQL> SELECT MYSEQ.CURRVAL,MYSEQ.NEXTVAL FROM DUAL;
   CURRVAL    NEXTVAL
         1          1
SQL>   SELECT LAST_NUMBER - INCREMENT_BY "Current value of x_seq" FROM USER_SEQUENCES
  2   WHERE SEQUENCE_NAME = 'MYSEQ';
Current value of x_seq
                     1
SQL>  SELECT MYSEQ.CURRVAL  FROM DUAL;
   CURRVAL
         1
SQL> SELECT MYSEQ.NEXTVAL FROM DUAL;
   NEXTVAL
         2
SQL>  SELECT LAST_NUMBER - INCREMENT_BY "Current value of x_seq" FROM USER_SEQUENCES
  2  WHERE SEQUENCE_NAME = 'MYSEQ';
Current value of x_seq
                     2
SQL>  SELECT MYSEQ.CURRVAL  FROM DUAL;
   CURRVAL
         2
SQL> disconnect
Disconnected from Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - 64bit Production
With the Partitioning, Oracle Label Security, OLAP and Data Mining options
SQL> connect scott
Enter password: *****
Connected.
SQL> r
  1*  SELECT MYSEQ.CURRVAL  FROM DUAL
SELECT MYSEQ.CURRVAL  FROM DUAL
ERROR at line 1:
ORA-08002: sequence MYSEQ.CURRVAL is not yet defined in this session
SQL>  SELECT LAST_NUMBER - INCREMENT_BY "Current value of x_seq" FROM USER_SEQUENCES
  2  WHERE SEQUENCE_NAME = 'MYSEQ';
Current value of x_seq
                     2