dolphindb支持列表查询吗

Question

我想立即应用下面的一组SQL语句并合并结果，以获得不同交易场所和市场类型(由'c1'，'c2'，'c3'，'4'标识(的各种股票(由'symbol'标识(的mt=52355979后面的最新记录。

select * from t where symbol=`A,c1=25,c2=814,c3=11,c4=2, date=2020.02.05, mt<52355979 order by mt desc limit 1
select * from t where symbol=`B,c1=25,c2=814,c3=12,c4=2, date=2020.02.05, mt<52355979 order by mt desc limit 1
select * from t where symbol=`C,c1=25,c2=814,c3=12,c4=2, date=2020.02.05, mt<52354979 order by mt desc limit 1
select * from t where symbol=`A,c1=1180,c2=333,c3=3,c4=116, date=2020.02.05, mt<52355979 order by mt desc limit 1

where条件中的筛选器列不会更改，而筛选器值可能每次都会更改。DolphindB是否提供允许使用不同输入参数运行列表查询的查询方法？

Answer 1

您可以如下定义函数

def bundleQuery(tbl, dt, dtColName, mt, mtColName, filterColValues, filterColNames){
cnt = filterColValues[0].size()
filterColCnt =filterColValues.size()
orderByCol = sqlCol(mtColName)
selCol = sqlCol("*")
filters = array(ANY, filterColCnt + 2)
filters[filterColCnt] = expr(sqlCol(dtColName), ==, dt)
filters[filterColCnt+1] = expr(sqlCol(mtColName), <, mt)

queries = array(ANY, cnt)
for(i in 0:cnt) {
for(j in 0:filterColCnt){
filters[j] = expr(sqlCol(filterColNames[j]), ==, filterColValues[j][i])
}
queries.append!(sql(select=selCol, from=tbl, where=filters, orderBy=orderByCol, ascOrder=false, limit=1))
}
return loop(eval, queries).unionAll(false)
}

然后使用以下脚本

dt = 2020.02.05
dtColName = "dsl"
mt = 52355979
mtColName = "mt"
colNames = `symbol`c1`c2`c3`c4
colValues = [50982208 50982208 51180116 41774759, 25 25 25 1180, 814 814 814 333, 11 12 12 3, 2 2 2 116]
bundleQuery(t, dt, dtColName, mt, mtColName, colValues, colNames)