Hi Atul, going back to your original code here could you try using variable for your generated SQL and then printing it out (or looking at it in the debugger).

e.g.

var sql = 'SELECT * FROM ' + Importantdata+
            +'where import_date between {ts \''+m_fro_date+'\'}' +' and {ts \'' +currentInsertDate+'\' }';
console.log(sql);
LABKEY.Query.executeSql({
               schemaName: 'DEMOSCHEMA',
               sql: sql,
        success: function(data){
        alert("YES!!");
      }
});

It would be helpful to know the exact SQL you are generating.