Menu
I have an MS Access database (intolerably enough), and communicating with it through PHP (ODBC).
There is a DateTime field that I have to include in my INSERT statement. This field is NOT defined as "Required" in Access, meaning that it is indeed NULL-able, and in fact some of the rows in the Access database are already NULL.
The problem I'm having is simple: How to insert NULL through SQL? All the results I've found online have addressed it from something like Visual Basic or C#, whereas I'm using SQL through ODBC in PHP.
I have already tried the following:
INSERT INTO table_name (datetime_field) VALUES (NULL)
INSERT INTO table_name (datetime_field) VALUES (#NULL#)
INSERT INTO table_name (datetime_field) VALUES ('NULL')
INSERT INTO table_name (datetime_field) VALUES ('#NULL#')
INSERT INTO table_name (datetime_field) VALUES ('')
(There's about 30 other columns in my query.)
The exact error I get is 'Data type mismatch in criteria expression' when I try '' or NULL. The others return a parse error (understandably).
Please note that I have to include the field in the INSERT statement. The field has a default value, but in many cases the original data that I'm transporting has a NULL that must also be a NULL in the target database.
Thanks in advance!
548
DateTime CAN be compared to null; It cannot hold null value, thus the comparison will always be false. DateTime is a "Value Type". Basically a "value type" can't set to NULL.
When you need to insert a null value into a column in an Access database, you could use "" to indicate a zero-length string. However, a zero-length string is not the same as Null. To insert a Null value, simple pass the keyword Null for the column, as shown in the code example.
You can insert NULL value into an int column with a condition i.e. the column must not have NOT NULL constraints. The syntax is as follows. INSERT INTO yourTableName(yourColumnName) values(NULL); To understand the above syntax, let us first create a table.
"NULL" can be specified as a value in the Date field to get an empty/blank by using INSERT statement. Example: CREATE table test1 (col1 date); INSERT into test1 values (NULL);
Try the following. It works for me:
INSERT INTO sometable ( somedate, somethingelse )
SELECT Null AS Expr1, "foo" AS Expr2;
Basically, you are wrapping the null in the select query and letting SQL figure out how to represent it to the insert.
-- EDIT --
This SHOULD also work:
INSERT INTO sometable ( somedate, somethingelse )
values (Null , "foo");
But for some reason it doesn't with my default install.
On I hunch, I switched my DB from ANSI-89 to ANSI-92, and the VALUES method started working. I switched it back to ANSI-89, and it still works. Not only that, on ANY new database I create, it now also works. Weird... something in the installation must be getting changed, (and sticking) by the switching back and forth that's not just ANSI-89/92. This seems to be why we were getting different results.
You can switch the database ocwe by going to Office Logo->Access Options->OBJECT DESIGNERS->QUERY DESIGN. Change SQL Server Compatible Syntax (ANSI 92) - and checking "This database".
Ok, very odd.
184
I know you've already figured this out but there is also dbNull
24
INSERT INTO table_name (datetime_field) VALUES (DbNull.Value)
36
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
