According to the query result align by device, can the query results of some devices be removed according to certain condition in Apache IoTDB? For example, I only want to query the data of fans 1-20 from hundreds of fans in total, and I cannot filter the data according to the fan numbers. I tried the following query statement, but the result still returns hundreds of data lines while I only want the first 20 lines.
Anyone know how to edit this statement?
select LAST_VALUE(heapId) as heapId,LAST_VALUE(bunchNo) as bunchNo,LAST_VALUE(no) as no, LAST_VALUE(voltage) as voltage,LAST_VALUE(temperature) as temperature,LAST_VALUE(soc) as soc,LAST_VALUE(soh) as soh from root.station01.cell.bms795717935384768512.bunch01.** where no > 0 and no <=20 align by device
Your SQL query will indeed remove rows where the last value of heapId is null, but this isn't effective at reducing the amount of data retrieved from the disk or network as this filtering is done after the fact.