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