不使用JOIN查询多个数据库表？

Question

我试图将三个查询合并为一个并且悲惨地失败。一切顺利，直到我通过＆＃34;添加＆＃34;顺序。子句。

SELECT
wti.price, hh.price, mb.price
FROM
spotprices.wti, spotprices.hh, spotprices.mb
ORDER BY
wti.sdate desc limit 1, hh.sdate desc limit 1, mb.sdate desc limit 1;

本质上，我试图通过sdate desc limit 1＆＃34;使用＆＃34;命令来获得sdate的最新价格。特技。单独地，查询效果很好。

SELECT price FROM spotprices.wti ORDER BY wti.sdate desc LIMIT 1;

Answer 1

使用select中的子查询：

SELECT (SELECT wti.price FROM spotprices.wti ORDER BY wti.sdate DESC LIMIT 1) as wti_price,
       (SELECT hh.price FROM spotprices.hh ORDER BY hh.sdate DESC LIMIT 1) as hh_price,
       (SELECT mb.price FROM spotprices.mb ORDER BY mb.sdate DESC LIMIT 1) as mb_price;