Hotfix/sangshuduo/td 12648 taosdump json null (#9526)

* [TD-12648]<fix>(tools): taosdump json null

* [TD-12648]<fix>(tools): taosdump json null

taos-tools @ dd78bfff

-Subproject commit 5881030ca50a263f6285ae38b4d3aeb1c8fcf8f2
+Subproject commit dd78bfff5549c08153798719c1707ab441b5f4ab

tests/develop-test/5-taos-tools/taosdump/taosdumpTestTypeJson.py

@@ -61,6 +61,16 @@ class TDTestCase:
             "create table t1 using st tags('{\"location\": \"beijing\"}')")
         tdSql.execute("insert into t1 values(1500000000000, 1)")
 
+        tdSql.execute(
+            "create table t2 using st tags(NULL)")
+        tdSql.execute("insert into t2 values(1500000000000, NULL)")
+
+        tdSql.execute(
+            "create table t3 using st tags('')")
+        tdSql.execute("insert into t3 values(1500000000000, 0)")
+
+#        sys.exit(1)
+
         buildPath = self.getBuildPath()
         if (buildPath == ""):
             tdLog.exit("taosdump not found!")
@@ -90,11 +100,11 @@ class TDTestCase:
         tdSql.checkData(0, 0, 'st')
 
         tdSql.query("show tables")
-        tdSql.checkRows(1)
-        tdSql.checkData(0, 0, 't1')
+        tdSql.checkRows(3)
+        tdSql.checkData(0, 0, 't3')
 
         tdSql.query("select jtag->'location' from st")
-        tdSql.checkRows(1)
+        tdSql.checkRows(3)
         tdSql.checkData(0, 0, "\"beijing\"")
 
         tdSql.query("select * from st where jtag contains 'location'")
@@ -102,6 +112,12 @@ class TDTestCase:
         tdSql.checkData(0, 1, 1)
         tdSql.checkData(0, 2, '{\"location\":\"beijing\"}')
 
+        tdSql.query("select jtag from st")
+        tdSql.checkRows(3)
+        tdSql.checkData(0, 0, "{\"location\":\"beijing\"}")
+        tdSql.checkData(1, 0, None)
+        tdSql.checkData(2, 0, None)
+
     def stop(self):
         tdSql.close()
         tdLog.success("%s successfully executed" % __file__)