- Postgres Generated By Default As Identity Primary Key
- Db2 Generated By Default
- Generated By Default As Identity Primary Key Examples
![Primary Primary](/uploads/1/2/5/7/125753581/285203506.png)
Your database provider typically takes care of the necessary configuration; for example, a numeric primary key in SQL Server is automatically set up to be an IDENTITY column. You can configure any property to have its value generated for inserted entities as follows.
You can create an IDENTITY column when you create a table, or change an existing table to add an IDENTITY column using ALTER TABLE..ADD. In either case, choose one of the IDENTITY statements described below. This section describes creating a table with an IDENTITY column.
Here is the formal syntax for creating a table with an IDENTITY column: The optional sequence_options
refer to all of the Sequence Generator attributes you can supply, and are described here: Sequence Generator Attributes . IDENTITY Column Statement | Description |
---|---|
GENERATED ALWAYS AS IDENTITY | The sequence generator always supplies an IDENTITY value. You cannot specify a value for the column. |
GENERATED BY DEFAULT AS IDENTITY | The sequence generator supplies an IDENTITY value any time you do not supply a column value. |
GENERATED BY DEFAULT ON NULL AS IDENTITY | The sequence generator supplies the next IDENTITY value if you specify a NULL columnn value. |
To create a table with a column
GENERATED ALWAYS AS IDENTITY
from the SQL CLI: For this table, tname1
, each time you add a row to the table, the Sequence Generator (SG) updates the idvalue
from its cache. You cannot specify a value for idValue
. If you do not specify any sequence generator attributes, the SG uses its default values, as described here: Sequence Generator Attributes . To create a table with a column GENERATED BY DEFAULT ON NULL AS IDENTITY:
Postgres Generated By Default As Identity Primary Key
For this table,
tname2
, each time you add a row, the SG inserts the next available value from its cache if no value is supplied for the idvalue
column, the supplied value for the idvalue
column is NULL. To create a table with a column GENERATED BY DEFAULT AS IDENTITY:
For this table,
tname3
, each time you add a row, the SG inserts the next available value from its cache if no value is supplied for the idvalue
column. To create a new table,
sg_atts
, with several SG attributes: Db2 Generated By Default
The tableGenerated By Default As Identity Primary Key Examples
sg_atts
specifies that the integer IDENTITY field (id
) is generated always. SG Attribute | Description |
---|---|
start with 2 | Start the sequence value at 2. |
increment by 2 | Increment the sequence value by 2 for each row. |
maxvalue 200 | Specifies the maximum IDENTITY value. What you specify overrides the default value maxvalue, which is the upper bound of the IDENTITY datatype in use. Once the IDENTITY column reaches this value, 200, the SG will not generate any more IDENTITY values. The maximum value has been reached and the no cycle attribute is in use. |
no cycle | Do not restart from 2 or with any value at all, once the column reaches the maxvalue . |
sg_some_atts
, with some SG attributes: For the sg_some_atts
table, specify an id
column GENERATED BY DEFAULT AS IDENTITY
, but which is not the primary key. SG Attribute or Other Detail | Description |
---|---|
CYCLE | Specifying CYCLE indicates that the SG should supply IDENTITY values up to either the MAXVALUE attribute you specify, or the default MAXVALUE . When the IDENTITY reaches the MAXVALUE value, the SG restarts the values over, beginning with MINVALUE , if it is specified, or with the default MINVALUE for the data type. CYCLE is orthogonal to the CACHE attribute, which indicates only how many values to store in local cache for swift access. You can set CACHE value to closely reflect the maximum value of the datatype, but we do not recommend this, due to the client cache size. |
CACHE 200 | The number of values that each client stores in its cache for fast retrieval. When the IDENTITY reaches the last number in the cache, the SG gets another set of values from the server automatically. |
START WITH 1 | The SG generates values 1, 2, 3 and so on, until it reaches the maximum value for a LONG data type. |
INCREMENT BY 1 | The SG increments each new IDENTITY value for every new row. |
Antares mic modeler vst download. For a full list of all sequence generator attributes, see Sequence Generator Attributes .