Syntax:
ALTER TABLE {TABLENAME}
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL}
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES
Example:
ALTER TABLE SomeTable
ADD SomeCol Bit NULL --Or NOT NULL.
CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.
Notes:
Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol
then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6
Optional With-Values Statement:
The WITH VALUES
is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL
, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES
or not.
How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable
and do not Specify SomeCol
's value, then it will Default to 0
.
If you insert a Record and Specify SomeCol
's value as NULL
(and your column allows nulls),
then the Default-Constraint will not be used and NULL
will be inserted as the Value.
Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.
SELECT owner, table_name
FROM dba_tables
This is assuming that you have access to the DBA_TABLES
data dictionary view. If you do not have those privileges but need them, you can request that the DBA explicitly grants you privileges on that table, or, that the DBA grants you the SELECT ANY DICTIONARY
privilege or the SELECT_CATALOG_ROLE
role (either of which would allow you to query any data dictionary table). Of course, you may want to exclude certain schemas like SYS
and SYSTEM
which have large numbers of Oracle tables that you probably don't care about.
Alternatively, if you do not have access to DBA_TABLES
, you can see all the tables that your account has access to through the ALL_TABLES
view:
SELECT owner, table_name
FROM all_tables
Although, that may be a subset of the tables available in the database (ALL_TABLES
shows you the information for all the tables that your user has been granted access to).
If you are only concerned with the tables that you own, not those that you have access to, you could use USER_TABLES
:
SELECT table_name
FROM user_tables
Since USER_TABLES
only has information about the tables that you own, it does not have an OWNER
column – the owner, by definition, is you.
Oracle also has a number of legacy data dictionary views-- TAB
, DICT
, TABS
, and CAT
for example-- that could be used. In general, I would not suggest using these legacy views unless you absolutely need to backport your scripts to Oracle 6. Oracle has not changed these views in a long time so they often have problems with newer types of objects. For example, the TAB
and CAT
views both show information about tables that are in the user's recycle bin while the [DBA|ALL|USER]_TABLES
views all filter those out. CAT
also shows information about materialized view logs with a TABLE_TYPE
of "TABLE" which is unlikely to be what you really want. DICT
combines tables and synonyms and doesn't tell you who owns the object.
Best Answer
There is no such thing as "auto_increment" or "identity" columns in Oracle as of Oracle 11g. However, you can model it easily with a sequence and a trigger:
Table definition:
Trigger definition:
UPDATE:
IDENTITY
column is now available on Oracle 12c:or specify starting and increment values, also preventing any insert into the identity column (
GENERATED ALWAYS
) (again, Oracle 12c+ only)Alternatively, Oracle 12 also allows to use a sequence as a default value: