I am interested in saving a group of process variables to a data store, and sele

Do you have a column which is a primary key for the table? If yes, you can use the primary key value to delete a record. In the XSD of your CDT you can annotate the primary key by using @Id. For more on such annotations you can refer Appian documentation - forum.appian.com/.../Defining_a_Custom_Data_Type

No, the 24 pages of documentation didn't quite answer my question. I will keep working on it until I find a solution.

Michael, here's an example of an XSD snippet where an "id" field of a CDT is marked as the primary key:
<xsd:element name="id" type="xsd:int">
<xsd:annotation>
<xsd:appinfo source="appian.jpa">
@Id
@GeneratedValue
</xsd:appinfo>
</xsd:annotation>
</xsd:element>

You need the annotation with an appinfo that has "appian.jpa" as its source. @Id indicates that this field is a PK. This is the minimum that you need in order to correctly update your rows in the DB using the Write to Data Store Entity smart service, and to delete rows using the Delete from Data Store Entities smart service.

@GeneratedValue is useful if you want your primary key values to be auto-generated each time you insert a row into the DB using the Write to DS smart service. It's a commonly used configuration.

After you've updated your XSD and reimported your CDT (forum.appian.com/.../Managing_Custom_Data_Types, the "id" field will now be the PK field.

Once you have the CDT set up with a primary key mapping, and you've republished your Data Store, you can try using the Write to DS node to create a row. Save the node output into a PV and check that the "id" field (or whichever field you marked as your PK field) and make sure it has the generated id if you're using @GeneratedValue.

Then modify the CDT value and call the Write to DS node again, with the id field populated with the id of the row that you want to update. Similarly, use the same id with the Delete from DS node.

Let us know if you need clarification on any of the above!

Annalise,
That's quite helpful! I'm getting a much more exciting class of error messages now.
Thanks for your guidance and assistance.
Mike

You're welcome! We should be able to help sort out the error messages if you don't have it working yet. Let us know how it goes.

Here's the start of my schema. It ignores the @ID etc and generates a_id anyway:
xsd:schema
targetNamespace="scrippsnetworksdev.appiancloud.com/.../"
xmlns:types611="scrippsnetworksdev.appiancloud.com/.../" xmlns:xsd="www.w3.org/.../XMLSchema">
<xsd:complexType name="RR_Resource">
<xsd:annotation>
<xsd:documentation><![CDATA[The CDT to contain information for all employees.]]></xsd:documentation>
</xsd:annotation>
<xsd:sequence>
<xsd:element name="empID_Int" nillable="true" type="xsd:int"/>
<xsd:annotation>
<xsd:appinfo source="appian.jpa">
@Id
@GeneratedValue
</xsd:appinfo>
</xsd:annotation>
<xsd:element name="employee_ID" nillable="true" type="xsd:int"/>

When I import the xsd file I receive this error message at the bottom of the Preview and Confirm New Data Types box:
XSD Parsing Message: XSD: The element 'www.w3.org/.../XMLSchema is not permitted as constrained by 'www.w3.org/.../XMLSchema expecting any | sequence | choice | group | element | nothing (APNX-2-4047-000)

In your example, you have a closing tag in both the empID_int and employee_ID elements.

The annotation needs to be *within* the element that you want to mark as the PK.

<xsd:element name... >
<xsd:annotation>

</xsd:annotation>
</xsd:element>

Notice how your "<xsd:element name..." ends with "/>" instead of ">". Here's an updated snippet:

<xsd:element name="empID_Int" nillable="true" type="xsd:int">
<xsd:annotation>
<xsd:appinfo source="appian.jpa">
@Id
@GeneratedValue
</xsd:appinfo>
</xsd:annotation>
</xsd:element>