2011-03-06 92 views
1

我有4个不同的表;每个都有自己的DATETIME彼此独立。什么是MySQL查询来获得MAX查询中的所有日期?MySQL:来自多个表的最大日期列

t1: DATE_TIME 
t2: DATE_TIME 
t3: DATE_TIME 
t4: DATE_TIME 

期望的结果

--------------------------------------------------------- 
| max_t1_date | max_t2_date | max_t3_date | max_t4_date | 
--------------------------------------------------------- 

回答

1

这已经有一段时间,因为我用的MySQL语法,我不能在此刻试试这个,但这应该工作:

SELECT 
    (SELECT MAX(date_time) FROM t1) AS max_t1_date, 
    (SELECT MAX(date_time) FROM t2) AS max_t2_date, 
    (SELECT MAX(date_time) FROM t3) AS max_t3_date, 
    (SELECT MAX(date_time) FROM t4) AS max_t4_date 
+0

谢谢!有效。 – sqlseeker 2011-03-06 06:40:15

1
SELECT t1.MaxDate max_t1_date, 
    t2.MaxDate max_t2_date, 
    t3.MaxDate max_t3_date, 
    t4.MaxDate max_t4_date 
FROM (SELECT MAX(DATE_TIME) MaxDate FROM t1) t1 
    (SELECT MAX(DATE_TIME) MaxDate FROM t2) t2, 
    (SELECT MAX(DATE_TIME) MaxDate FROM t3) t3, 
    (SELECT MAX(DATE_TIME) MaxDate FROM t4) t4 
2

许多这种方法来剥皮这只猫...

SELECT max(t1.a) AS max_table1date, 
     max(t2.a) AS max_table2date, 
     max(t3.a) AS max_table3date 
    FROM table1 t1, 
     table2 t2, 
     table3 t3