diff --git a/packages/builder/src/components/backend/DataTable/modals/CreateEditRow.svelte b/packages/builder/src/components/backend/DataTable/modals/CreateEditRow.svelte
index 5929b2db96..790a74df53 100644
--- a/packages/builder/src/components/backend/DataTable/modals/CreateEditRow.svelte
+++ b/packages/builder/src/components/backend/DataTable/modals/CreateEditRow.svelte
@@ -29,6 +29,12 @@
       // Prevent modal closing if there were errors
       return false
     }
+
+    if (rowResponse.status === 500) {
+      notifier.danger(rowResponse.message)
+      return false
+    }
+
     notifier.success("Row saved successfully.")
     backendUiStore.actions.rows.save(rowResponse)
   }
diff --git a/packages/server/src/constants/index.js b/packages/server/src/constants/index.js
index ff2e6f19f0..90893730be 100644
--- a/packages/server/src/constants/index.js
+++ b/packages/server/src/constants/index.js
@@ -12,6 +12,11 @@ exports.FieldTypes = {
   AUTO: "auto",
 }
 
+exports.RelationshipTypes = {
+  ONE_TO_MANY: "one-to-many",
+  MANY_TO_MANY: "many-to-many",
+}
+
 exports.AuthTypes = {
   APP: "app",
   BUILDER: "builder",
diff --git a/packages/server/src/db/linkedRows/LinkController.js b/packages/server/src/db/linkedRows/LinkController.js
index f51454d9e8..b01d5eede5 100644
--- a/packages/server/src/db/linkedRows/LinkController.js
+++ b/packages/server/src/db/linkedRows/LinkController.js
@@ -2,7 +2,7 @@ const CouchDB = require("../index")
 const { IncludeDocs, getLinkDocuments } = require("./linkUtils")
 const { generateLinkID } = require("../utils")
 const Sentry = require("@sentry/node")
-const { FieldTypes } = require("../../constants")
+const { FieldTypes, RelationshipTypes } = require("../../constants")
 const { isEqual } = require("lodash")
 
 /**
@@ -163,8 +163,30 @@ class LinkController {
             ? linkDoc.doc2.rowId
             : linkDoc.doc1.rowId
         })
+
+        // if 1:N, ensure that this ID is not already attached to another record
+        const linkedTable = await this._db.get(field.tableId)
+        const linkedSchema = linkedTable.schema[field.fieldName]
+
         // iterate through the link IDs in the row field, see if any don't exist already
         for (let linkId of rowField) {
+          if (linkedSchema.relationshipType === RelationshipTypes.ONE_TO_MANY) {
+            const links = await getLinkDocuments({
+              appId: this._appId,
+              tableId: field.tableId,
+              rowId: linkId,
+              includeDocs: IncludeDocs.INCLUDE,
+            })
+
+            // The 1 side of 1:N is already related to something else
+            // You must remove the existing relationship
+            if (links.length > 0) {
+              throw new Error(
+                `1:N Relationship Error: Record already linked to another.`
+              )
+            }
+          }
+
           if (linkId && linkId !== "" && linkDocIds.indexOf(linkId) === -1) {
             // first check the doc we're linking to exists
             try {