diff --git a/src/DIRAC/Core/Utilities/MySQL.py b/src/DIRAC/Core/Utilities/MySQL.py
index 25f282ad985..712b8fdf5de 100755
--- a/src/DIRAC/Core/Utilities/MySQL.py
+++ b/src/DIRAC/Core/Utilities/MySQL.py
@@ -1042,7 +1042,7 @@ def _createTables(self, tableDict, force=False):
                         # cmdList.append( '`%s` %s' % ( forTable, tableDict[forTable]['Fields'][forKey] )
                         cmdList.append(
                             "FOREIGN KEY ( `%s` ) REFERENCES `%s` ( `%s` )"
-                            " ON DELETE RESTRICT" % (key, forTable, forKey)
+                            " ON DELETE CASCADE" % (key, forTable, forKey)
                         )
 
                 engine = thisTable.get("Engine", "InnoDB")
diff --git a/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.py b/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.py
index 5e66cd54a0b..d3962300456 100755
--- a/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.py
+++ b/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.py
@@ -193,19 +193,13 @@ def deletePilots(self, pilotIDs, conn=False):
         if not isinstance(pilotIDs, list):
             return S_ERROR("Input argument is not a List")
 
-        failed = []
-
         result = self._escapeValues(pilotIDs)
         if not result["OK"]:
             return S_ERROR(f"Failed to remove pilot: {result['Value']}")
         stringIDs = ",".join(result["Value"])
-        for table in ["PilotOutput", "JobToPilotMapping", "PilotAgents"]:
-            result = self._update(f"DELETE FROM {table} WHERE PilotID in ({stringIDs})", conn=conn)
-            if not result["OK"]:
-                failed.append(table)
-
-        if failed:
-            return S_ERROR(f"Failed to remove pilot from {', '.join(failed)} tables")
+        result = self._update(f"DELETE FROM PilotAgents WHERE PilotID in ({stringIDs})", conn=conn)
+        if not result["OK"]:
+            return S_ERROR("Failed to remove pilots: ", result["Message"])
         return S_OK(pilotIDs)
 
     ##########################################################################################
diff --git a/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.sql b/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.sql
index 7168e529f74..3756c498a32 100755
--- a/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.sql
+++ b/src/DIRAC/WorkloadManagementSystem/DB/PilotAgentsDB.sql
@@ -54,8 +54,8 @@ CREATE TABLE `JobToPilotMapping` (
   `PilotID` INT(11) UNSIGNED NOT NULL,
   `JobID` INT(11) UNSIGNED NOT NULL,
   `StartTime` DATETIME NOT NULL,
-  KEY `JobID` (`JobID`),
-  KEY `PilotID` (`PilotID`)
+  PRIMARY KEY (`PilotID`, `JobID`),
+  FOREIGN KEY (`PilotID`) REFERENCES `PilotAgents`(`PilotID`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
 
 DROP TABLE IF EXISTS `PilotOutput`;
@@ -63,5 +63,6 @@ CREATE TABLE `PilotOutput` (
   `PilotID` INT(11) UNSIGNED NOT NULL,
   `StdOutput` MEDIUMTEXT,
   `StdError` MEDIUMTEXT,
-  PRIMARY KEY (`PilotID`)
+  PRIMARY KEY (`PilotID`),
+  FOREIGN KEY (`PilotID`) REFERENCES `PilotAgents`(`PilotID`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
diff --git a/src/DIRAC/WorkloadManagementSystem/DB/SandboxMetadataDB.py b/src/DIRAC/WorkloadManagementSystem/DB/SandboxMetadataDB.py
index 639beb8afeb..cbedcad1bad 100644
--- a/src/DIRAC/WorkloadManagementSystem/DB/SandboxMetadataDB.py
+++ b/src/DIRAC/WorkloadManagementSystem/DB/SandboxMetadataDB.py
@@ -60,10 +60,11 @@ def __initializeDB(self):
             "Fields": {
                 "SBId": "INTEGER(10) UNSIGNED NOT NULL",
                 "EntityId": "VARCHAR(128) NOT NULL",
-                "Type": "VARCHAR(64) NOT NULL",
+                "Type": "ENUM('Input', 'Output') NOT NULL",
             },
             "Indexes": {"Entity": ["EntityId"], "SBIndex": ["SBId"]},
             "UniqueIndexes": {"Mapping": ["SBId", "EntityId", "Type"]},
+            "ForeignKeys": {"SBId": "sb_SandBoxes.SBId"},
         }
 
         for tableName in self.__tablesDesc:
@@ -323,12 +324,8 @@ def deleteSandboxes(self, SBIdList):
         Delete sandboxes
         """
         sqlSBList = ", ".join([str(sbid) for sbid in SBIdList])
-        for table in ("sb_SandBoxes", "sb_EntityMapping"):
-            sqlCmd = f"DELETE FROM `{table}` WHERE SBId IN ( {sqlSBList} )"
-            result = self._update(sqlCmd)
-            if not result["OK"]:
-                return result
-        return S_OK()
+        sqlCmd = f"DELETE FROM sb_SandBoxes WHERE SBId IN ( {sqlSBList} )"
+        return self._update(sqlCmd)
 
     def getSandboxId(self, SEName, SEPFN, requesterName, requesterGroup, field="SBId", requesterDN=None):
         """
diff --git a/src/DIRAC/WorkloadManagementSystem/DB/TaskQueueDB.py b/src/DIRAC/WorkloadManagementSystem/DB/TaskQueueDB.py
index f235c50ac2a..5a023aa70b1 100755
--- a/src/DIRAC/WorkloadManagementSystem/DB/TaskQueueDB.py
+++ b/src/DIRAC/WorkloadManagementSystem/DB/TaskQueueDB.py
@@ -319,18 +319,7 @@ def cleanOrphanedTaskQueues(self, connObj=False):
         if not orphanedTQs:
             return S_OK()
         orphanedTQs = [str(otq[0]) for otq in orphanedTQs]
-
-        for mvField in multiValueDefFields:
-            result = self._update(
-                f"DELETE FROM `tq_TQTo{mvField}` WHERE TQId in ( {','.join(orphanedTQs)} )", conn=connObj
-            )
-            if not result["OK"]:
-                return result
-
-        result = self._update(f"DELETE FROM `tq_TaskQueues` WHERE TQId in ( {','.join(orphanedTQs)} )", conn=connObj)
-        if not result["OK"]:
-            return result
-        return S_OK()
+        return self._update(f"DELETE FROM `tq_TaskQueues` WHERE TQId in ( {','.join(orphanedTQs)} )", conn=connObj)
 
     def __setTaskQueueEnabled(self, tqId, enabled=True, connObj=False):
         if enabled:
@@ -990,10 +979,6 @@ def deleteTaskQueueIfEmpty(self, tqId, tqOwner=False, tqOwnerGroup=False, connOb
         tqToDel = retVal["Value"]
 
         if tqToDel:
-            for mvField in multiValueDefFields:
-                retVal = self._update(f"DELETE FROM `tq_TQTo{mvField}` WHERE TQId = {tqId}", conn=connObj)
-                if not retVal["OK"]:
-                    return retVal
             retVal = self._update(f"DELETE FROM `tq_TaskQueues` WHERE TQId = {tqId}", conn=connObj)
             if not retVal["OK"]:
                 return retVal
diff --git a/tests/Integration/WorkloadManagementSystem/Test_SandboxMetadataDB.py b/tests/Integration/WorkloadManagementSystem/Test_SandboxMetadataDB.py
index 6da5c5303f7..1b8f0a5872a 100644
--- a/tests/Integration/WorkloadManagementSystem/Test_SandboxMetadataDB.py
+++ b/tests/Integration/WorkloadManagementSystem/Test_SandboxMetadataDB.py
@@ -28,7 +28,7 @@ def test_SandboxMetadataDB():
     print(f"sbId:{sbId}")
     print(f"newSandbox:{newSandbox}")
 
-    assignTo = {owner: [(f"SB:{sbSE}|{sbPFN}", ownerGroup)]}
+    assignTo = {123: [(f"SB:{sbSE}|{sbPFN}", "Input")]}
     res = smDB.assignSandboxesToEntities(assignTo, owner, ownerGroup)
     assert res["OK"], res["Message"]
     assert res["Value"] == 1