说输入：
表t1

row_num_unimportant   indicator
        1                 111
        2                 222

表t2

row_num_unimportant   indicator   val_timestamp   val_of_interest2
        1                 112       timestamp2        value1
        2                 113       timestamp1        value3
        3                 114       timestamp3        value2
        4                 223       timestamp4        value5
        5                 224       timestamp5        value4

我想看看结果

indicator    min_timestamp    val_of_interest2
   111         timestamp1          value3
   222         timestamp4          value5

困难在于有兴趣值2与最小时间戳相关。
天真地说：

SELECT
  indicator,
  MIN(val_timestamp) AS min_timestamp,
  ???? AS val_of_interest2
FROM (
  SELECT
    t1.indicator,
    t2.val_timestamp,
    t2.val_of_interest2
  FROM
    T1 t1
    JOIN T2 t2
    ON (t2.indicator >= t1.indicator)
)
GROUP BY
  indicator

基本上，我应该把什么放在？？？部分(或者我需要一个不同的查询吗？）
谢谢！