Check Dialog v9
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.
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.
Use the fields in the General
tab to identify the check constraint:
- Use the
Name
field to provide a descriptive name for the check constraint that will be displayed in theBrowser
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. - Store notes about the check constraint in the
Comment
field.
Click the Definition
tab to continue.
Use the fields in the Definition
tab to define the check constraint:
- Provide the expression that a row must satisfy in the
Check
field. - Move the
No Inherit?
switch to theYes
position to specify this constraint is automatically inherited by a table's children. The default isNo
. - Move the
Don't validate?
switch to theNo
position to skip validation of existing data; the constraint may not hold for all rows in the table. The default isYes
.
Click the SQL
tab to continue.
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.
Example
The following is an example of the sql command generated by user selections in the Check
dialog:
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.
- Click the
Info
button (i) to access online help. View context-sensitive help in theTabbed browser
, where a new tab displays the PostgreSQL core documentation. - Click the
Save
button to save work. - Click the
Cancel
button to exit without saving work. - Click the
Reset
button to restore configuration parameters.