pgadmin4/docs/en_US/primary_key_dialog.rst

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.. _primary_key_dialog:
2018-06-15 03:14:12 -05:00
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`Primary key Dialog`:index:
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Use the *Primary key* dialog to create or modify a primary key constraint. A
primary key constraint indicates that a column, or group of columns, uniquely
identifies rows in a table. This requires that the values in the selected
column(s) be both unique and not null.
The *Primary key* dialog organizes the development of a primary key constraint
through the *General* and *Definition* tabs. The *SQL* tab displays the SQL code
generated by dialog selections.
.. image:: images/primary_key_general.png
:alt: Primary key dialog general tab
:align: center
Use the fields in the *General* tab to identify the primary key:
* Use the *Name* field to add a descriptive name for the primary key constraint.
The name will be displayed in the *pgAdmin* tree control.
Click the *Definition* tab to continue.
.. image:: images/primary_key_definition.png
:alt: Primary key dialog definition tab
:align: center
Use the fields in the *Definition* tab to define the primary key constraint:
* Click inside the *Columns* field and select one or more column names from the
drop-down listbox. To delete a selection, click the *x* to the left of the
column name. The primary key constraint should be different from any unique
constraint defined for the same table; the selected column(s) for the
constraints must be distinct.
* Use *Include columns* field to specify columns for *INCLUDE* clause of the
index. This option is available in Postgres 11 and later.
* Select the name of the tablespace in which the primary key constraint will
reside from the drop-down listbox in the *Tablespace* field.
* Select the name of an index from the drop-down listbox in the *Index* field.
This field is optional. Adding a primary key will automatically create a
unique B-tree index on the column or group of columns listed in the primary
key, and will force the column(s) to be marked NOT NULL.
* Use the *Fill Factor* field to specify a fill factor for the table and index.
The fill factor for a table is a percentage between 10 and 100. 100 (complete
packing) is the default.
* Move the *Deferrable?* switch to the *Yes* position to specify the timing of
the constraint is deferrable and can be postponed until the end of the
statement. The default is *No*.
* If enabled, move the *Deferred?* switch to the *Yes* position to specify the
timing of the constraint is deferred to the end of the statement. The default
is *No*.
Click the *SQL* tab to continue.
Your entries in the *Primary key* dialog generate a SQL command (see an example
below). Use the *SQL* tab for review; revisit or switch tabs to make any changes
to the SQL command.
Example
*******
The following is an example of the sql command generated by user selections in
the *Primary key* dialog:
.. image:: images/primary_key_sql.png
:alt: Primary key dialog sql tab
:align: center
The example shown demonstrates creating a primary key constraint named
*jobhist_pk* on the *empno* column of the *jobhist* table.
* Click the *Info* button (i) to access online help.
* Click the *Save* button to save work.
* Click the *Close* button to exit without saving work.
* Click the *Reset* button to restore configuration parameters.