Re: [GENERAL] Default column value
| От | David G. Johnston |
|---|---|
| Тема | Re: [GENERAL] Default column value |
| Дата | |
| Msg-id | CAKFQuwZa6K0qamC_YuoFZhKwgbTMokd2V8xpCS7yYStpR-wxsg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: [GENERAL] Default column value (Rich Shepard <rshepard@appl-ecosys.com>) |
| Ответы |
Re: [GENERAL] Default column value [ANSWERED]
|
| Список | pgsql-general |
On Fri, 30 Dec 2016, Adrian Klaver wrote:DEFAULT is what is the column is set to if the user does not specify a
value. As shown above a user can supply a NULL value. To guard against
that the NOT NULL constraint is required.
One more case I'd appreciate being clarified: when the column's value has
a check constraint with acceptable values in a list. For example,
param_units VARCHAR(8) DEFAULT 'mg/L'
CONSTRAINT param_units
CHECK (param_units IN ('ppm', 'mg/L', 'ug/L', 'umho/cm', 'percent', 'cfm', 'gpm')),
Seems to me that if values are constrained by a list a NULL cannot be
entered by the user. Is this correct?
"The CHECK clause specifies an expression producing a Boolean result which new or updated rows must satisfy for an insert or update operation to succeed. Expressions evaluating to TRUE or UNKNOWN succeed."
NULL == "UNKNOWN"
David J.
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