dolphindb中的concatDateTime(date, time)函数可以满足上面的场景，示例如下：
select concatDateTime(date,time) as datetime, sym, qty, price from t;
结果如下：
请问dolphindb中如何把date和time合并为1列datetime？
假如我现在的表结构如下：
date=[2019.06.18, 2019.06.20, 2019.06.21, 2019.06.19, 2019.06.18, 2019.06.20] time = [09:34:07,09:36:42,09:36:51,09:36:59,09:32:47,09:35:26] sym = `C`MS`MS`MS`IBM`IBM$SYMBOL price= 49.6 29.46 29.52 30.02 174.97 175.23 qty = 2200 1900 2100 3200 6800 5400 t = table(date, time, sym, qty, price);
我现在想把date和time合并为1列datetime，请问应该怎么实现？