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46 lines
2.3 KiB
ReStructuredText
46 lines
2.3 KiB
ReStructuredText
.. _check_dialog:
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****************
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The Check Dialog
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****************
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Use the *Check* dialog to define or modify a check constraint. A check constraint specifies an expression that produces a Boolean result that new or 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 *General* and *Definition* tabs. The *SQL* tab displays the SQL code generated by dialog selections.
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.. image:: images/check_general.png
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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 add a descriptive name for the check constraint. The name will be displayed in the *pgAdmin* tree control. With PostgreSQL 9.5 forward, when a table has multiple check constraints, they will be tested for each row in alphabetical order by name and after NOT NULL constraints.
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Click the *Definition* tab to continue.
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.. image:: images/check_definition.png
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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 this constraint is automatically inherited by a table's children. The default is *No*.
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* Move the *Don't validate?* switch to the *No* position to skip validation of existing data; the constraint may not hold for all rows in the table. The 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 below). Use the *SQL* tab for review; revisit or switch tabs to make any changes 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 the *Check* dialog:
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.. image:: images/check_sql.png
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The example shown demonstrates creating a check constraint named *check_price* on the *price* column of the *products* table. The constraint confirms that any values added to the column are greater than 0.
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* Click the *Info* button (i) to access online help. View context-sensitive help in the *Tabbed browser*, where a new tab displays the PostgreSQL core documentation.
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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.
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