Null is converted to empty string when writing to database.

RE: Null is converted to empty string when writing to database.

davel001150 — Tue, 12 May 2020 13:41:42 GMT

One fun thing you can do is run it through filternulls() after you have it out of the query. It shouldn't be THAT much overhead to return a list of nulls from your query, but "IS NULL" and "IS NOT NULL" should be fine if you are querying an integer row.

Perhaps wrapping the query in toInteger() would also help. That should at least theoretically convert null type Text into null type Integer.

RE: Null is converted to empty string when writing to database.

AK47 — Tue, 12 May 2020 13:00:14 GMT

How to do similar thing for Integer? If an integer field is empty or null, I don't want it return in query

RE: Null is converted to empty string when writing to database.

davel001150 — Fri, 10 Apr 2020 16:18:41 GMT

Aparently ORACLE won't let you have that problem, which may be why this is the first I've ever heard of it

RE: Null is converted to empty string when writing to database.

daniels0003 — Wed, 08 Apr 2020 15:31:03 GMT

Thanks Philip. For some reason this didn't work for me when comparing to null, but it pointed me in the right direction. I ended up using the "queryLogicalExpression" function to do something like this:

a!queryLogicalExpression(
  operator: "OR",
  filters: {
    a!queryFilter(
      field: "name",
      operator: "is null"
    ),
    a!queryFilter(
      field: "name",
      operator: "in",
      value: {""}
    )
  }
)

RE: Null is converted to empty string when writing to database.

Philip Snyman — Thu, 10 Oct 2019 16:50:22 GMT

An easy workaround to query entities with empty ( null ) text fields is to use the following query filter:

a!queryFilter(
    field: "name",
    operator: "in",
    value: {"", null}
)

RE: Null is converted to empty string when writing to database.

sergeiz — Thu, 15 Nov 2018 08:20:47 GMT

Right, I never experience that before with appian 16.3 and 17.4. I didn't do anything specific to prevent that because I never experience that. :)

My text columns are defined in Oracle as VARCHAR2, I saw nillable="true" attribute in CDT xsd, but it works without this attribute.

RE: Null is converted to empty string when writing to database.

Mike Schmitt — Wed, 14 Nov 2018 14:28:06 GMT

I've run into this issue before, too - it's particularly aggravating because a!queryEntity filters with the "is null" operator don't work as expected when the database field is empty text but not "null"; and Appian seemingly provides no way (without severe workarounds anyway) to put "null" as the value in a field that previously held a value - something that could potentially be a common use case.

RE: Null is converted to empty string when writing to database.

Jerry Sylveus — Wed, 14 Nov 2018 13:07:08 GMT

Hi Sergeiz,
Are you saying that you have not experienced that issue before? If so, is there anything specific that you are doing to prevent that?

RE: Null is converted to empty string when writing to database.

sergeiz — Wed, 14 Nov 2018 10:34:17 GMT

I didn't see such issues.

Can you put here the definition of database column and of CDT column.

RE: Null is converted to empty string when writing to database.

sahithip120 — Wed, 14 Nov 2018 00:08:34 GMT

Hi Varsha,

You can handle this is the CDT annotations

RE: Null is converted to empty string when writing to database.

Chris — Tue, 13 Nov 2018 17:49:03 GMT

Another option would be to utilize a trigger on the DB table that converts empty values to null, which can run automatically after each INSERT or UPDATE.

RE: Null is converted to empty string when writing to database.

mitchellg942045 — Tue, 13 Nov 2018 17:03:37 GMT

In addition to the alternatives suggested, you could enforce the logic on the SQL side by always excluding empty string values from the column.

RE: Null is converted to empty string when writing to database.

bradc0001 — Mon, 12 Nov 2018 21:51:00 GMT

Hi Varsha,

From my experience, Appian will always write a blank value instead of null of data type Text. The workarounds I have used in the past are:

Following the writeToDataStoreEntity node, use a Query Database node with a statement such as UPDATE table SET col1 = NULL WHERE col1 = ''
If this particular value is always blank/null, you can exclude it from your CDT so that Appian does not replace is with a blank value.

I realize these solutions are less than ideal, and I do wish Appian would treat text fields the same as other data types and retain a NULL value in the database. I am curious if anyone else has come up with a better solution.

Brad