Oracle Practical 16
CREATION OF SEQUENCES AND
SYNONYMS
Sequences
Use Sequences to assign unique values, like an AutoNumber in MS Access. The syntax
is as follows…
CREATE SEQUENCE seqname
INCREMENT BY integer
START WITH integer
MAXVALUE integer
MINVALUE integer
CYCLE
CACHE integer
ORDER
/
-- or NOCYCLE
-- or NOCACHE
-- or NOORDER
SEQUENCE – the name you give the sequence generator
INCREMENT BY – this refers to the interval between sequence numbers (does the
number increment by 2 or 5 for example. The default is 1.)
START WITH – what number does the sequence start at (default is 1)
MAXVALUE – the maximum value that the sequence can generate
MINVALUE – the minimum value that the sequence can generate
CYCLE – this refers to whether the numbers in the sequence are re-cycled when the
maximum value is reached.
CACHE - specifies how many values the Oracle Server will pre-allocate and keep in
memory.
ORDER – the order in which the numbers are allocated
To use a sequence, you use the following syntax…
SELECT
FROM
seq_tdb_log.nextval
dual;
Seq_tdb_log – this is the
name of the sequence
being called. Nextval is a
pseudocolumn.
See USER_SEQUENCES for data dictionary information on sequences.
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Oracle Practical 16
Synonyms
“A word having the same or nearly the same meaning as another word or other words in
a language.” So we can query SCOTT.EMP, if we have been granted select on that
table…
SELECT
FROM
*
scott.emp;
Typing SCOTT every time we query one of his tables is annoying; we should create a
synonym for the table.
CREATE SYNONYM emp FOR scott.emp
/
Now we can omit ‘SCOTT.’.
To help others we may want t make this synonym available to everyone, by making it
public.
CREATE PUBLIC SYNONYM emp FOR scott.emp
/
Now every user account within this database can refer to that table without specifying
the user.
See USER_SYNONYMS for data dictionary information.
Recommended Books for those interested in pursuing Oracle in their Careers, Not
required:
“Oracle: The complete reference”. (Latest edition, Oracle Press).
“Oracle: PL/SQL Programming”. (Latest edition, Oracle Press).
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