diff --git a/source/libs/executor/src/timesliceoperator.c b/source/libs/executor/src/timesliceoperator.c
index 2698b0bfd951a701d4364d5c0312f256136cfdc1..4348bce1b8f4af05916429003b1a6ee1194acd8f 100644
--- a/source/libs/executor/src/timesliceoperator.c
+++ b/source/libs/executor/src/timesliceoperator.c
@@ -271,15 +271,27 @@ static bool genInterpolationResult(STimeSliceOperatorInfo* pSliceInfo, SExprSupp
 
         if (pDst->info.type == TSDB_DATA_TYPE_FLOAT) {
           float v = 0;
-          GET_TYPED_DATA(v, float, pVar->nType, &pVar->i);
+          if (!IS_VAR_DATA_TYPE(pVar->nType)) {
+            GET_TYPED_DATA(v, float, pVar->nType, &pVar->i);
+          } else {
+            v = taosStr2Float(varDataVal(pVar->pz), NULL);
+          }
           colDataSetVal(pDst, rows, (char*)&v, false);
         } else if (pDst->info.type == TSDB_DATA_TYPE_DOUBLE) {
           double v = 0;
-          GET_TYPED_DATA(v, double, pVar->nType, &pVar->i);
+          if (!IS_VAR_DATA_TYPE(pVar->nType)) {
+            GET_TYPED_DATA(v, double, pVar->nType, &pVar->i);
+          } else {
+            v = taosStr2Double(varDataVal(pVar->pz), NULL);
+          }
           colDataSetVal(pDst, rows, (char*)&v, false);
         } else if (IS_SIGNED_NUMERIC_TYPE(pDst->info.type)) {
           int64_t v = 0;
-          GET_TYPED_DATA(v, int64_t, pVar->nType, &pVar->i);
+          if (!IS_VAR_DATA_TYPE(pVar->nType)) {
+            GET_TYPED_DATA(v, int64_t, pVar->nType, &pVar->i);
+          } else {
+            v = taosStr2int64(varDataVal(pVar->pz));
+          }
           colDataSetVal(pDst, rows, (char*)&v, false);
         } else if (IS_BOOLEAN_TYPE(pDst->info.type)) {
           bool v = false;
diff --git a/source/libs/parser/src/parTranslater.c b/source/libs/parser/src/parTranslater.c
index 285102beeb209608401d65641bfefe18bfbca039..2a586a44a2ad7863ed5bbb08159a33ae48eba71e 100644
--- a/source/libs/parser/src/parTranslater.c
+++ b/source/libs/parser/src/parTranslater.c
@@ -1523,11 +1523,6 @@ static int32_t translateInterpFunc(STranslateContext* pCxt, SFunctionNode* pFunc
   SSelectStmt* pSelect = (SSelectStmt*)pCxt->pCurrStmt;
   SNode*       pTable = pSelect->pFromTable;
 
-  if ((NULL != pTable && QUERY_NODE_REAL_TABLE != nodeType(pTable))) {
-    return generateSyntaxErrMsgExt(&pCxt->msgBuf, TSDB_CODE_PAR_ONLY_SUPPORT_SINGLE_TABLE,
-                                   "%s is only supported in single table query", pFunc->functionName);
-  }
-
   if (pSelect->hasAggFuncs || pSelect->hasMultiRowsFunc || pSelect->hasIndefiniteRowsFunc) {
     return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_NOT_ALLOWED_FUNC);
   }
diff --git a/tests/system-test/2-query/interp.py b/tests/system-test/2-query/interp.py
index cdbfa0de84ad51dbbbf5e9146ce43797cf13e5b8..6630713f73389f4fabe2f6542f3c89c7da982638 100644
--- a/tests/system-test/2-query/interp.py
+++ b/tests/system-test/2-query/interp.py
@@ -38,6 +38,8 @@ class TDTestCase:
 
         tdLog.printNoPrefix("==========step2:insert data")
 
+        tdSql.execute(f"use db")
+
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:05', 5, 5, 5, 5, 5.0, 5.0, true, 'varchar', 'nchar')")
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:10', 10, 10, 10, 10, 10.0, 10.0, true, 'varchar', 'nchar')")
         tdSql.execute(f"insert into {dbname}.{tbname} values ('2020-02-01 00:00:15', 15, 15, 15, 15, 15.0, 15.0, true, 'varchar', 'nchar')")
@@ -182,6 +184,35 @@ class TDTestCase:
         tdSql.checkData(2, 0, 1)
         tdSql.checkData(3, 0, 1)
 
+        ## test fill value with string
+        tdSql.query(f"select interp(c0) from {dbname}.{tbname} range('2020-02-01 00:00:16', '2020-02-01 00:00:19') every(1s) fill(value, 'abc')")
+        tdSql.checkRows(4)
+        tdSql.checkData(0, 0, 0)
+        tdSql.checkData(1, 0, 0)
+        tdSql.checkData(2, 0, 0)
+        tdSql.checkData(3, 0, 0)
+
+        tdSql.query(f"select interp(c0) from {dbname}.{tbname} range('2020-02-01 00:00:16', '2020-02-01 00:00:19') every(1s) fill(value, '123')")
+        tdSql.checkRows(4)
+        tdSql.checkData(0, 0, 123)
+        tdSql.checkData(1, 0, 123)
+        tdSql.checkData(2, 0, 123)
+        tdSql.checkData(3, 0, 123)
+
+        tdSql.query(f"select interp(c0) from {dbname}.{tbname} range('2020-02-01 00:00:16', '2020-02-01 00:00:19') every(1s) fill(value, '123.123')")
+        tdSql.checkRows(4)
+        tdSql.checkData(0, 0, 123)
+        tdSql.checkData(1, 0, 123)
+        tdSql.checkData(2, 0, 123)
+        tdSql.checkData(3, 0, 123)
+
+        tdSql.query(f"select interp(c0) from {dbname}.{tbname} range('2020-02-01 00:00:16', '2020-02-01 00:00:19') every(1s) fill(value, '12abc')")
+        tdSql.checkRows(4)
+        tdSql.checkData(0, 0, 12)
+        tdSql.checkData(1, 0, 12)
+        tdSql.checkData(2, 0, 12)
+        tdSql.checkData(3, 0, 12)
+
         tdLog.printNoPrefix("==========step5:fill prev")
 
         ## {. . .}
@@ -2916,6 +2947,24 @@ class TDTestCase:
         tdLog.printNoPrefix("======step 14: test interp pseudo columns")
         tdSql.error(f"select _irowts, c6 from {dbname}.{tbname}")
 
+        tdLog.printNoPrefix("======step 15: test interp in nested query")
+        tdSql.query(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{stbname}) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+        tdSql.query(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1}) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{stbname}) partition by tbname range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1}) partition by tbname range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union select * from {dbname}.{ctbname2}) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union select * from {dbname}.{ctbname2} order by ts) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union all select * from {dbname}.{ctbname2}) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union all select * from {dbname}.{ctbname2} order by ts) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union all select * from {dbname}.{ctbname2}) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+        tdSql.error(f"select _irowts, _isfilled, interp(c0) from (select * from {dbname}.{ctbname1} union all select * from {dbname}.{ctbname2} order by ts) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
+        tdSql.query(f"select _irowts, _isfilled, interp(c0) from (select {ctbname1}.ts,{ctbname1}.c0 from {dbname}.{ctbname1}, {dbname}.{ctbname2} where {ctbname1}.ts = {ctbname2}.ts) range('2020-02-01 00:00:00', '2020-02-01 00:00:14') every(1s) fill(null)")
+
     def stop(self):
         tdSql.close()
         tdLog.success(f"{__file__} successfully executed")