//call analytical functions within SQL statements



schema = extractTextSchema("c:/DolphinDB/Data/USstocks.csv")
update schema set type=`DOUBLE where name=`RET
USstocks = ploadText("c:/DolphinDB/Data/USstocks.csv", , schema);

t=select date, VOL\SHROUT as turnover, abs(RET) as absRet, (ASK-BID)/(BID+ASK)*2 as spread, log(SHROUT*(BID+ASK)/2) as logMV from USstocks where VOL>0
beta = select ols(turnover, (absRet,spread), 1, 2).Coefficient.beta as ``absRet`spread from t group by date
plot(select absRet,spread from beta, beta.date);