diff --git a/tests/system-test/2-query/union.py b/tests/system-test/2-query/union.py
index 96c29a2222..e359164a4f 100644
--- a/tests/system-test/2-query/union.py
+++ b/tests/system-test/2-query/union.py
@@ -231,30 +231,31 @@ class TDTestCase:
                     tdSql.execute(f"{sqls[j+i]} union {sqls[i]}")
                 else:
                     tdSql.error(f"{sqls[i]} union {sqls[j+i]}")
+
         # check union with timeline function
-        tdSql.query(f"select first(c1) from (select * from t1 union select * from t1 order by ts)")
+        tdSql.query(f"select first(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts)")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 9)
-        tdSql.query(f"select last(c1) from (select * from t1 union select * from t1 order by ts desc)")
+        tdSql.query(f"select last(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts desc)")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 2147450880)
-        tdSql.query(f"select irate(c1) from (select * from t1 union select * from t1 order by ts)")
+        tdSql.query(f"select irate(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts)")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 9.102222222222222)
-        tdSql.query(f"select elapsed(ts) from (select * from t1 union select * from t1 order by ts)")
+        tdSql.query(f"select elapsed(ts) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts)")
         tdSql.checkRows(1)
         tdSql.checkData(0, 0, 46800000.000000000000000)
-        tdSql.query(f"select diff(c1) from (select * from t1 union select * from t1 order by ts)")
+        tdSql.query(f"select diff(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts)")
         tdSql.checkRows(14)
-        tdSql.query(f"select derivative(c1, 1s, 0) from (select * from t1 union select * from t1 order by ts)")
+        tdSql.query(f"select derivative(c1, 1s, 0) from (select * from {dbname}.t1 union select * from {dbname}.t1 order by ts)")
         tdSql.checkRows(11)
 
-        tdSql.error(f"select first(c1) from (select * from t1 union select * from t1)")
-        tdSql.error(f"select last(c1) from (select * from t1 union select * from t1)")
-        tdSql.error(f"select irate(c1) from (select * from t1 union select * from t1)")
-        tdSql.error(f"select elapsed(ts) from (select * from t1 union select * from t1)")
-        tdSql.error(f"select diff(c1) from (select * from t1 union select * from t1)")
-        tdSql.error(f"select derivative(c1, 1s, 0) from (select * from t1 union select * from t1)")
+        tdSql.error(f"select first(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
+        tdSql.error(f"select last(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
+        tdSql.error(f"select irate(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
+        tdSql.error(f"select elapsed(ts) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
+        tdSql.error(f"select diff(c1) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
+        tdSql.error(f"select derivative(c1, 1s, 0) from (select * from {dbname}.t1 union select * from {dbname}.t1)")
 
 
     def __test_error(self, dbname="db"):