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66 lines
2.5 KiB
ReStructuredText
66 lines
2.5 KiB
ReStructuredText
.. _check_dialog:
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*********************
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`Check Dialog`:index:
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*********************
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Use the *Check* dialog to define or modify a check constraint. A check
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constraint specifies an expression that produces a Boolean result that new or
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updated rows must satisfy for an insert or update operation to succeed.
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The *Check* dialog organizes the development of a check constraint through the
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*General* and *Definition* tabs. The *SQL* tab displays the SQL code generated
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by dialog selections.
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.. image:: images/check_general.png
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:alt: Check dialog general tab
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:align: center
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Use the fields in the *General* tab to identify the check constraint:
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* Use the *Name* field to provide a descriptive name for the check constraint
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that will be displayed in the *pgAdmin* tree control. With PostgreSQL 9.5
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forward, when a table has multiple check constraints, they will be tested for
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each row in alphabetical order by name and after NOT NULL constraints.
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* Store notes about the check constraint in the *Comment* field.
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Click the *Definition* tab to continue.
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.. image:: images/check_definition.png
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:alt: Check dialog definition tab
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:align: center
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Use the fields in the *Definition* tab to define the check constraint:
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* Provide the expression that a row must satisfy in the *Check* field.
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* Move the *No Inherit?* switch to the *Yes* position to specify that this
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constraint is not automatically inherited by a table's children. The default
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is *No*, meaning that the constraint will be inherited by any children.
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* Move the *Don't validate?* switch to the *No* position to skip validation of
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existing data; the constraint may not hold for all rows in the table. The
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default is *Yes*.
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Click the *SQL* tab to continue.
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Your entries in the *Check* 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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The following is an example of the sql command generated by user selections in
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the *Check* dialog:
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.. image:: images/check_sql.png
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:alt: Check dialog sql tab
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:align: center
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The example shown demonstrates creating a check constraint named *check_price*
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on the *price* column of the *products* table. The constraint confirms that
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any values added to the column are greater than 0.
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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 *Cancel* button to exit without saving work.
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* Click the *Reset* button to restore configuration parameters. |