看看这个手册:元编程 (dolphindb.cn)
period=1..4
sqlColAlias(makeCall(rowAvg, sqlCol(take(`bid, size(period)) + string(period))), `bidavg)
返回结果是下面这句
< rowAvg([< bid1 >,< bid2 >,< bid3 >,< bid4 >]) as bidavg >
应该是rowavg不支持这个向量,下面这个可以
< rowAvg(bid1, bid2, bid3, bid4) as bidavg >
请问这种元语句该怎么写?