MySQL：来自多个表的最大日期列

Question

我有4张不同的桌子; 每个人都有自己独立的DATETIME。 在1个查询中获取MAX的所有日期的MySQL查询是什么？

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 |
---------------------------------------------------------

Answer 1

皮肤这种猫很多方法......

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

Answer 2

我使用MySQL语法已经有一段时间了，我现在不能尝试这个，但这应该有效：

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

Answer 3

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