Part1 create sequence,dual table

Part1 create sequence,dual table

• 1.
  Part 1- createsequence DUAL TABLE 1DR. GIRIJA NARASIMHAN
• 2.
  The DUAL tableis a special one-row, one-column table present by default in all Oracle database installations. DUAL is originally a table and the database engine would perform disk IO on the table when selecting from DUAL. This disk IO was usually logical IO (not involving physical disk access) as the disk blocks were usually already cached in memory. This resulted in a large amount of logical IO against the DUAL table. Beginning with 10g Release 1 Oracle Database have been optimized and the database no longer performs physical or logical IO on the DUAL table even though the DUAL table still actually exists. DUAL is readily available for all the users in database. It is not limited to system administrator only. 2DR. GIRIJA NARASIMHAN
• 3.
  DR. GIRIJA NARASIMHAN3 create sequence Syntax
• 4.
  SQL> create sequenceseq1 2 START WITH 1000 3 INCREMENT BY 1 4 NOCACHE 5 maxvalue 1005 6 cycle; Sequence created. 4
• 5.
  SQL> select seq1.nextvalfrom dual; NEXTVAL ---------- 1004 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1005 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1 SQL> select seq1.nextval from dual; NEXTVAL ---------- 2 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1000 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1001 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1002 SQL> select seq1.nextval from dual; NEXTVAL ---------- 1003 5DR. GIRIJA NARASIMHAN