--- a/db_schema/lada_schema.sql	Tue Nov 01 12:11:06 2016 +0100
+++ b/db_schema/lada_schema.sql	Tue Nov 01 12:47:25 2016 +0100
@@ -192,7 +192,7 @@
 
 CREATE TABLE probe (
     id serial PRIMARY KEY,
-    id_alt character varying(20) UNIQUE NOT NULL
+    id_alt character varying(16) UNIQUE NOT NULL
         DEFAULT 'sss'
             || lpad(nextval('land.probe_probe_id_seq')::varchar, 12, '0')
             || 'Y',

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main/java/de/intevation/lada/validation/rules/probe/UniqueIdAlt.java	Tue Nov 01 12:47:25 2016 +0100
@@ -0,0 +1,56 @@
+/* Copyright (C) 2013 by Bundesamt fuer Strahlenschutz
+ * Software engineering by Intevation GmbH
+ *
+ * This file is Free Software under the GNU GPL (v>=3)
+ * and comes with ABSOLUTELY NO WARRANTY! Check out
+ * the documentation coming with IMIS-Labordaten-Application for details.
+ */
+package de.intevation.lada.validation.rules.probe;
+
+import java.util.List;
+
+import javax.inject.Inject;
+
+import de.intevation.lada.model.land.Probe;
+import de.intevation.lada.util.annotation.RepositoryConfig;
+import de.intevation.lada.util.data.QueryBuilder;
+import de.intevation.lada.util.data.Repository;
+import de.intevation.lada.util.data.RepositoryType;
+import de.intevation.lada.validation.Violation;
+import de.intevation.lada.validation.annotation.ValidationRule;
+import de.intevation.lada.validation.rules.Rule;
+
+/**
+ * Validation rule for probe.
+ * Validates if the probe has a unique "id_alt".
+ *
+ */
+@ValidationRule("Probe")
+public class UniqueIdAlt implements Rule {
+
+    @Inject
+    @RepositoryConfig(type=RepositoryType.RO)
+    private Repository repo;
+
+    @Override
+    public Violation execute(Object object) {
+        Probe probe = (Probe)object;
+        QueryBuilder<Probe> builder = new QueryBuilder<Probe>(
+            repo.entityManager("land"),
+            Probe.class);
+        builder.and("idAlt", probe.getIdAlt());
+        List<Probe> existing = repo.filterPlain(builder.getQuery(), "land");
+        if (!existing.isEmpty()) {
+            Probe found = existing.get(0);
+            // The probe found in the db equals the new probe. (Update)
+            if (probe.getId() != null && probe.getId().equals(found.getId())) {
+                return null;
+            }
+            Violation violation = new Violation();
+            violation.addError("idAlt", 611);
+            return violation;
+        }
+        return null;
+    }
+
+}