diff --git a/full/Changes b/full/Changes
index 7620c38..1633dbb 100644
--- a/full/Changes
+++ b/full/Changes
@@ -7,6 +7,9 @@
 11/04/2019
    - Fixed unknown authentication scheme, missing VC entity, and parameter 
      checker (margaretha)
+   - Fixed sharing unknown VC, updating corpusQuery, and handling non-
+     unique group name and unknown VC access (margaretha)
+     
 
 # version 0.61.6
 04/02/2019
diff --git a/full/src/main/java/de/ids_mannheim/korap/dao/VirtualCorpusAccessDao.java b/full/src/main/java/de/ids_mannheim/korap/dao/VirtualCorpusAccessDao.java
index db49626..3b372ab 100644
--- a/full/src/main/java/de/ids_mannheim/korap/dao/VirtualCorpusAccessDao.java
+++ b/full/src/main/java/de/ids_mannheim/korap/dao/VirtualCorpusAccessDao.java
@@ -24,6 +24,8 @@
 import de.ids_mannheim.korap.entity.VirtualCorpusAccess_;
 import de.ids_mannheim.korap.entity.VirtualCorpus_;
 import de.ids_mannheim.korap.exceptions.KustvaktException;
+import de.ids_mannheim.korap.exceptions.StatusCodes;
+import de.ids_mannheim.korap.oauth2.constant.OAuth2Error;
 import de.ids_mannheim.korap.utils.ParameterChecker;
 
 /**
@@ -57,7 +59,14 @@
         query.where(
                 builder.equal(access.get(VirtualCorpusAccess_.id), accessId));
         Query q = entityManager.createQuery(query);
-        return (VirtualCorpusAccess) q.getSingleResult();
+        try{
+            return (VirtualCorpusAccess) q.getSingleResult();
+        }
+        catch (NoResultException e) {
+            throw new KustvaktException(StatusCodes.NO_RESOURCE_FOUND,
+                    "Virtual corpus access is not found",
+                    String.valueOf(accessId));
+        }
     }
 
     // for vca admins
diff --git a/full/src/main/java/de/ids_mannheim/korap/service/UserGroupService.java b/full/src/main/java/de/ids_mannheim/korap/service/UserGroupService.java
index e094c33..e06e9b2 100644
--- a/full/src/main/java/de/ids_mannheim/korap/service/UserGroupService.java
+++ b/full/src/main/java/de/ids_mannheim/korap/service/UserGroupService.java
@@ -1,5 +1,6 @@
 package de.ids_mannheim.korap.service;
 
+import java.sql.SQLException;
 import java.time.ZonedDateTime;
 import java.util.ArrayList;
 import java.util.Collections;
@@ -214,8 +215,26 @@
     public void createUserGroup (UserGroupJson groupJson, String createdBy)
             throws KustvaktException {
 
-        int groupId = userGroupDao.createGroup(groupJson.getName(), createdBy,
-                UserGroupStatus.ACTIVE);
+        int groupId=0;
+        try {
+            groupId = userGroupDao.createGroup(groupJson.getName(), createdBy,
+                    UserGroupStatus.ACTIVE);
+        }
+        // handle DB exceptions, e.g. unique constraint
+        catch (Exception e) {
+            Throwable cause = e;
+            Throwable lastCause = null;
+            while ((cause = cause.getCause()) != null
+                    && !cause.equals(lastCause)) {
+                if (cause instanceof SQLException) {
+                    break;
+                }
+                lastCause = cause;
+            }
+            throw new KustvaktException(StatusCodes.DB_INSERT_FAILED,
+                    cause.getMessage());
+        }
+        
         UserGroup userGroup = userGroupDao.retrieveGroupById(groupId);
 
         if (groupJson.getMembers() != null){
diff --git a/full/src/main/java/de/ids_mannheim/korap/service/VirtualCorpusService.java b/full/src/main/java/de/ids_mannheim/korap/service/VirtualCorpusService.java
index c0ba90b..187b738 100644
--- a/full/src/main/java/de/ids_mannheim/korap/service/VirtualCorpusService.java
+++ b/full/src/main/java/de/ids_mannheim/korap/service/VirtualCorpusService.java
@@ -255,7 +255,7 @@
         String koralQuery = null;
         CorpusAccess requiredAccess = null;
         String corpusQuery = newVC.getCorpusQuery();
-        if (corpusQuery != null && corpusQuery.isEmpty()) {
+        if (corpusQuery != null && !corpusQuery.isEmpty()) {
             koralQuery = serializeCorpusQuery(corpusQuery);
             requiredAccess = determineRequiredAccess(newVC.isCached(), vcName,
                     koralQuery);
@@ -428,6 +428,12 @@
             String groupName) throws KustvaktException {
 
         VirtualCorpus vc = vcDao.retrieveVCByName(vcName, createdBy);
+        if (vc == null){
+            String vcCode = createdBy + "/" + vcName;
+            throw new KustvaktException(StatusCodes.NO_RESOURCE_FOUND,
+                    "Virtual corpus "+ vcCode+" is not found.",
+                    String.valueOf(vcCode));
+        }
         if (!username.equals(vc.getCreatedBy())
                 && !adminDao.isAdmin(username)) {
             throw new KustvaktException(StatusCodes.AUTHORIZATION_FAILED,
diff --git a/full/src/test/java/de/ids_mannheim/korap/web/controller/VirtualCorpusControllerTest.java b/full/src/test/java/de/ids_mannheim/korap/web/controller/VirtualCorpusControllerTest.java
index ce5535a..53adca4 100644
--- a/full/src/test/java/de/ids_mannheim/korap/web/controller/VirtualCorpusControllerTest.java
+++ b/full/src/test/java/de/ids_mannheim/korap/web/controller/VirtualCorpusControllerTest.java
@@ -119,15 +119,17 @@
     public void testRetrieveSystemVCInfo () throws UniformInterfaceException,
             ClientHandlerException, KustvaktException {
 
-        JsonNode node = testSearchVC("VirtualCorpusControllerTest", "system", "system VC");
+        JsonNode node = testSearchVC("VirtualCorpusControllerTest", "system",
+                "system VC");
         assertEquals("system VC", node.at("/name").asText());
         assertEquals(VirtualCorpusType.SYSTEM.displayName(),
                 node.at("/type").asText());
     }
 
     @Test
-    public void testRetrieveOwnerPrivateVCInfo () throws UniformInterfaceException,
-            ClientHandlerException, KustvaktException {
+    public void testRetrieveOwnerPrivateVCInfo ()
+            throws UniformInterfaceException, ClientHandlerException,
+            KustvaktException {
 
         JsonNode node = testSearchVC("dory", "dory", "dory VC");
         assertEquals("dory VC", node.at("/name").asText());
@@ -199,14 +201,13 @@
         assertEquals("published VC", node.at("/name").asText());
         assertEquals(VirtualCorpusType.PUBLISHED.displayName(),
                 node.at("/type").asText());
-        
+
         // check gill in the hidden group of the vc
-        ClientResponse response = resource().path(API_VERSION).path("group").path("list")
-                .path("system-admin").queryParam("status", "HIDDEN")
-                .header(Attributes.AUTHORIZATION,
-                        HttpAuthorizationHandler
-                                .createBasicAuthorizationHeaderValue(
-                                        "admin", "pass"))
+        ClientResponse response = resource().path(API_VERSION).path("group")
+                .path("list").path("system-admin")
+                .queryParam("status", "HIDDEN")
+                .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
+                        .createBasicAuthorizationHeaderValue("admin", "pass"))
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
                 .get(ClientResponse.class);
 
@@ -241,17 +242,17 @@
     }
 
     @Test
-    public void testListAvailableVCByOtherUser () throws UniformInterfaceException,
-            ClientHandlerException, KustvaktException {
+    public void testListAvailableVCByOtherUser ()
+            throws UniformInterfaceException, ClientHandlerException,
+            KustvaktException {
         ClientResponse response = resource().path(API_VERSION).path("vc")
-                .path("dory")
-                .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
+                .path("dory").header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
                 .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
                         .createBasicAuthorizationHeaderValue("pearl", "pass"))
                 .get(ClientResponse.class);
         String entity = response.getEntity(String.class);
         JsonNode node = JsonUtils.readTree(entity);
-        
+
         assertEquals(Status.UNAUTHORIZED.getStatusCode(), response.getStatus());
         assertEquals(StatusCodes.AUTHORIZATION_FAILED,
                 node.at("/errors/0/0").asInt());
@@ -313,9 +314,9 @@
     public void testCreatePublishedVC () throws KustvaktException {
         String json = "{\"type\": \"PUBLISHED\""
                 + ",\"corpusQuery\": \"corpusSigle=GOE\"}";
-        
+
         String vcName = "new published vc";
-        
+
         ClientResponse response = resource().path(API_VERSION).path("vc")
                 .path("VirtualCorpusControllerTest").path(vcName)
                 .header(Attributes.AUTHORIZATION,
@@ -334,8 +335,8 @@
         assertEquals(vcName, node.get(0).get("name").asText());
 
         // EM: check hidden access
-        node = testlistAccessByGroup("admin","");
-        node = node.get(node.size()-1);
+        node = testlistAccessByGroup("admin", "");
+        node = node.get(node.size() - 1);
         assertEquals("system", node.at("/createdBy").asText());
         assertEquals(vcName, node.at("/vcName").asText());
         assertTrue(node.at("/userGroupName").asText().startsWith("auto"));
@@ -531,9 +532,9 @@
         assertEquals("corpusQuery is null", node.at("/errors/0/1").asText());
         assertEquals("corpusQuery", node.at("/errors/0/2").asText());
     }
-    
+
     @Test
-    public void testCreateVCWithoutEntity() throws KustvaktException {
+    public void testCreateVCWithoutEntity () throws KustvaktException {
         ClientResponse response = resource().path(API_VERSION).path("vc")
                 .path("VirtualCorpusControllerTest").path("new vc")
                 .header(Attributes.AUTHORIZATION,
@@ -554,8 +555,7 @@
 
     @Test
     public void testCreateVCWithoutType () throws KustvaktException {
-        String json = "{\"corpusQuery\": "
-                + "\"creationDate since 1820\"}";
+        String json = "{\"corpusQuery\": " + "\"creationDate since 1820\"}";
 
         ClientResponse response = resource().path(API_VERSION).path("vc")
                 .path("VirtualCorpusControllerTest").path("new vc")
@@ -601,7 +601,7 @@
                         + "VirtualCorpusType` from String \"PRIVAT\": value not one of "
                         + "declared Enum instance names"));
     }
-
+    
     @Test
     public void testDeleteVCUnauthorized () throws KustvaktException {
         ClientResponse response = resource().path(API_VERSION).path("vc")
@@ -650,8 +650,8 @@
         // 2nd edit
         json = "{\"description\": \"test vc\"}";
 
-        response = resource().path(API_VERSION).path("vc")
-                .path("dory").path("dory VC")
+        response = resource().path(API_VERSION).path("vc").path("dory")
+                .path("dory VC")
                 .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
                         .createBasicAuthorizationHeaderValue("dory", "pass"))
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
@@ -666,6 +666,29 @@
     }
 
     @Test
+    public void testEditCorpusQuery () throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
+        String json = "{\"corpusQuery\": \"corpusSigle=WPD17\"}";
+
+        ClientResponse response = resource().path(API_VERSION).path("vc")
+                .path("dory").path("dory VC")
+                .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
+                        .createBasicAuthorizationHeaderValue("dory", "pass"))
+                .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
+                .header(HttpHeaders.CONTENT_TYPE, ContentType.APPLICATION_JSON)
+                .put(ClientResponse.class, json);
+
+        assertEquals(Status.OK.getStatusCode(), response.getStatus());
+
+        // check VC
+        JsonNode node = testListVC("dory");
+        String koralQuery = node.get(0).get("koralQuery").asText();
+        node = JsonUtils.readTree(koralQuery);
+        assertEquals("WPD17", node.at("/collection/value").asText());
+        assertTrue(koralQuery.contains("WPD17"));
+    }
+
+    @Test
     public void testEditVCNotOwner () throws KustvaktException {
         String json = "{\"description\": \"edited vc\"}";
 
@@ -694,13 +717,13 @@
     @Test
     public void testPublishProjectVC () throws KustvaktException {
 
-        String vcName= "group VC";
-        
+        String vcName = "group VC";
+
         // check the vc type
         JsonNode node = testSearchVC("dory", "dory", vcName);
         assertEquals(VirtualCorpusType.PROJECT.displayName(),
                 node.get("type").asText());
-        
+
         // edit vc
         String json = "{\"type\": \"PUBLISHED\"}";
         ClientResponse response = resource().path(API_VERSION).path("vc")
@@ -721,7 +744,7 @@
         // check hidden VC access
         node = testlistAccessByGroup("admin", "");
         assertEquals(4, node.size());
-        node = node.get(node.size()-1);
+        node = node.get(node.size() - 1);
         assertEquals(vcName, node.at("/vcName").asText());
         assertEquals("system", node.at("/createdBy").asText());
         assertTrue(node.at("/userGroupName").asText().startsWith("auto"));
@@ -729,8 +752,8 @@
         // edit 2nd
         json = "{\"type\": \"PROJECT\"}";
 
-        response = resource().path(API_VERSION).path("vc")
-                .path("dory").path("group VC")
+        response = resource().path(API_VERSION).path("vc").path("dory")
+                .path("group VC")
                 .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
                         .createBasicAuthorizationHeaderValue("dory", "pass"))
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
@@ -757,29 +780,31 @@
                 node.at("/errors/0/1").asText());
     }
 
-//    @Test
-//    public void testlistAccessMissingId () throws KustvaktException {
-//        ClientResponse response = resource().path(API_VERSION).path("vc")
-//                .path("access")
-//                .header(Attributes.AUTHORIZATION,
-//                        HttpAuthorizationHandler
-//                                .createBasicAuthorizationHeaderValue(
-//                                        "VirtualCorpusControllerTest", "pass"))
-//                .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
-//                .get(ClientResponse.class);
-//        String entity = response.getEntity(String.class);
-//        JsonNode node = JsonUtils.readTree(entity);
-//        assertEquals(Status.BAD_REQUEST.getStatusCode(), response.getStatus());
-//        assertEquals(StatusCodes.MISSING_PARAMETER,
-//                node.at("/errors/0/0").asInt());
-//        assertEquals("vcId", node.at("/errors/0/1").asText());
-//    }
+    // @Test
+    // public void testlistAccessMissingId () throws KustvaktException
+    // {
+    // ClientResponse response =
+    // resource().path(API_VERSION).path("vc")
+    // .path("access")
+    // .header(Attributes.AUTHORIZATION,
+    // HttpAuthorizationHandler
+    // .createBasicAuthorizationHeaderValue(
+    // "VirtualCorpusControllerTest", "pass"))
+    // .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
+    // .get(ClientResponse.class);
+    // String entity = response.getEntity(String.class);
+    // JsonNode node = JsonUtils.readTree(entity);
+    // assertEquals(Status.BAD_REQUEST.getStatusCode(),
+    // response.getStatus());
+    // assertEquals(StatusCodes.MISSING_PARAMETER,
+    // node.at("/errors/0/0").asInt());
+    // assertEquals("vcId", node.at("/errors/0/1").asText());
+    // }
 
     @Test
     public void testlistAccessByGroup () throws KustvaktException {
         ClientResponse response = resource().path(API_VERSION).path("vc")
-                .path("access")
-                .queryParam("groupName", "dory group")
+                .path("access").queryParam("groupName", "dory group")
                 .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
                         .createBasicAuthorizationHeaderValue("dory", "pass"))
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
@@ -791,7 +816,7 @@
         assertEquals(2, node.at("/0/vcId").asInt());
         assertEquals("group VC", node.at("/0/vcName").asText());
         assertEquals(2, node.at("/0/userGroupId").asInt());
-        
+
         assertEquals("dory group", node.at("/0/userGroupName").asText());
     }
 
@@ -801,19 +826,20 @@
 
         String vcName = "marlin VC";
         String groupName = "marlin group";
-        
+
         // check the vc type
         JsonNode node = testSearchVC("marlin", "marlin", vcName);
         assertEquals(vcName, node.at("/name").asText());
         assertEquals("private", node.at("/type").asText());
-        
-        ClientResponse response = testShareVCByCreator("marlin", vcName, groupName);
+
+        ClientResponse response =
+                testShareVCByCreator("marlin", vcName, groupName);
         assertEquals(Status.OK.getStatusCode(), response.getStatus());
 
         // check the vc type
         node = testSearchVC("marlin", "marlin", vcName);
         assertEquals("project", node.at("/type").asText());
-        
+
         // list vc access by marlin
         node = testlistAccessByGroup("marlin", groupName);
         assertEquals(2, node.size());
@@ -830,19 +856,19 @@
 
         // delete access by vc-admin
         // dory is a vc-admin in marlin group
-        testDeleteAccess("dory", accessId);
+        response = testDeleteAccess("dory", accessId);
+        assertEquals(Status.OK.getStatusCode(), response.getStatus());
 
         // list vc access by dory
         node = testlistAccessByGroup("dory", groupName);
         assertEquals(1, node.size());
-        
+
         testEditVCType("marlin", "marlin", vcName, VirtualCorpusType.PRIVATE);
     }
 
-
-    private ClientResponse testShareVCByCreator (String vcCreator, String vcName, String groupName)
-            throws UniformInterfaceException, ClientHandlerException,
-            KustvaktException {
+    private ClientResponse testShareVCByCreator (String vcCreator,
+            String vcName, String groupName) throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
 
         return resource().path(API_VERSION).path("vc").path(vcCreator)
                 .path(vcName).path("share").path(groupName)
@@ -852,29 +878,52 @@
                 .post(ClientResponse.class);
     }
 
-    private void testShareVCNonUniqueAccess (String vcCreator, String vcName, String groupName)
-            throws UniformInterfaceException, ClientHandlerException,
-            KustvaktException {
-        ClientResponse response = testShareVCByCreator(vcCreator, vcName, groupName);
+    private void testShareVCNonUniqueAccess (String vcCreator, String vcName,
+            String groupName) throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
+        ClientResponse response =
+                testShareVCByCreator(vcCreator, vcName, groupName);
         JsonNode node = JsonUtils.readTree(response.getEntity(String.class));
         assertEquals(HttpStatus.SC_BAD_REQUEST, response.getStatus());
         assertEquals(StatusCodes.DB_INSERT_FAILED,
                 node.at("/errors/0/0").asInt());
-        
+
         // EM: message differs depending on the database used
         // for testing. The message below is from sqlite.
-//        assertTrue(node.at("/errors/0/1").asText()
-//                .startsWith("[SQLITE_CONSTRAINT_UNIQUE]"));
+        // assertTrue(node.at("/errors/0/1").asText()
+        // .startsWith("[SQLITE_CONSTRAINT_UNIQUE]"));
     }
 
     @Test
-    public void testShareVCByVCAAdmin ()
-            throws UniformInterfaceException, ClientHandlerException,
-            KustvaktException {
+    public void testShareUnknownVC () throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
+        ClientResponse response = testShareVCByCreator("marlin",
+                "non-existing-vc", "marlin group");
+        JsonNode node = JsonUtils.readTree(response.getEntity(String.class));
+        assertEquals(HttpStatus.SC_NOT_FOUND, response.getStatus());
+        assertEquals(StatusCodes.NO_RESOURCE_FOUND,
+                node.at("/errors/0/0").asInt());
+    }
+
+    @Test
+    public void testShareUnknownGroup () throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
+        ClientResponse response = testShareVCByCreator("marlin", "marlin VC",
+                "non-existing-group");
+        JsonNode node = JsonUtils.readTree(response.getEntity(String.class));
+        assertEquals(HttpStatus.SC_NOT_FOUND, response.getStatus());
+        assertEquals(StatusCodes.NO_RESOURCE_FOUND,
+                node.at("/errors/0/0").asInt());
+    }
+
+    @Test
+    public void testShareVCByVCAAdmin () throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
 
         // dory is VCA in marlin group
         ClientResponse response = resource().path(API_VERSION).path("vc")
-                .path("marlin").path("marlin VC").path("share").path("marlin group")
+                .path("marlin").path("marlin VC").path("share")
+                .path("marlin group")
                 .header(Attributes.AUTHORIZATION, HttpAuthorizationHandler
                         .createBasicAuthorizationHeaderValue("dory", "pass"))
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
@@ -910,7 +959,7 @@
                 node.at("/errors/0/1").asText());
     }
 
-    private void testDeleteAccess (String username, String accessId)
+    private ClientResponse testDeleteAccess (String username, String accessId)
             throws UniformInterfaceException, ClientHandlerException,
             KustvaktException {
         ClientResponse response = resource().path(API_VERSION).path("vc")
@@ -920,7 +969,7 @@
                 .header(HttpHeaders.X_FORWARDED_FOR, "149.27.0.32")
                 .delete(ClientResponse.class);
 
-        assertEquals(Status.OK.getStatusCode(), response.getStatus());
+        return response;
     }
 
     private void testDeleteAccessUnauthorized (String accessId)
@@ -945,4 +994,14 @@
                 "Unauthorized operation for user: VirtualCorpusControllerTest",
                 node.at("/errors/0/1").asText());
     }
+
+    @Test
+    public void testDeleteNonExistingAccess () throws UniformInterfaceException,
+            ClientHandlerException, KustvaktException {
+        ClientResponse response = testDeleteAccess("dory", "100");
+        assertEquals(Status.NOT_FOUND.getStatusCode(), response.getStatus());
+
+        JsonNode node = JsonUtils.readTree(response.getEntity(String.class));
+        assertEquals(StatusCodes.NO_RESOURCE_FOUND, node.at("/errors/0/0").asInt());
+    }
 }