我对sql中的一个子查询有一点小问题。answers a where a.id = g.maxid limit 1) as subquery left join answers agroup by g.id order by finished DESC;
我希望该子查询返回来自所以我尝试在子查询中使用sel
(复数),而不使用子查询?该表包含以下数据(对不起,鼠标四个):如您所见,我总是希望选择最小值。如果存在相同的值(表2和表3),则查询将给出所有行,因为没有最小值。我使用的是MySQL。如果可能的话,出于性能原因,我不想使用子查询。min(值)和group by id也不起作用,因为id是唯一的。宁斯基
在环顾四周并按照在上给出的答案后,我尝试了这个查询。SELECT * FROM book, category WHERE book.category=category.id AND book.id IN (SELECT book.id FROM bookORDER BY rating LIMIT 3) #1235 - This version of MySQL doesn't yet support 'LIMIT &IN/ALL/ANY
discussion AS d ORDER BY ( SELECT (1) AS itemFROM messages AS m WHERE m.discussion = idDisc GROUP BY m.user) DESC 当我执行此SQL当我通过直接在查询中完成ID来运行子查询时,它不适用于COUNT:
SELECT COUNT(*) AS t
如果我在where子句中应用静态数据,它比应用子查询更快。示例:SELECT STARTDATE, ENDDATE FROM TEST WHERE STARTDATE = '2012-08-21';SELECTSTARTDATE, ENDDATE FROM TEST WHERE STARTDATE = (SELECT STARTDATE FROM TEST2 LIMIT 1);
或者他们在任何情况下都是一样的子<