I have a form on a website which has a lot of different fields. Some of the fields are optional while some are mandatory. In my DB I have a table which holds all these values, is it better practice to insert a NULL value or an empty string into the DB columns where the user didn't put any data?
By using NULL
you can distinguish between "put no data" and "put empty data".
Some more differences:
A LENGTH
of NULL
is NULL
, a LENGTH
of an empty string is 0
.
NULL
s are sorted before the empty strings.
COUNT(message)
will count empty strings but not NULL
s
You can search for an empty string using a bound variable but not for a NULL
. This query:
SELECT *
FROM mytable
WHERE mytext = ?
will never match a NULL
in mytext
, whatever value you pass from the client. To match NULL
s, you'll have to use other query:
SELECT *
FROM mytable
WHERE mytext IS NULL