我有一张这样的表
ts item infoA infoB
2018-02-03 12:00:00 A null null
2018-02-03 12:01:00 null A1 null
2018-02-03 12:02:00 A null null
2018-02-03 12:03:00 null null null
2018-02-03 12:04:00 null A2 null
2018-02-03 12:05:00 null null null
2018-02-03 12:06:00 B null null
2018-02-03 12:07:00 null null B1
2018-02-03 12:08:00 null null null
我想仅在相关项
上用时间序列填充空数据ts item infoA infoB
2018-02-03 12:00:00 A null null
2018-02-03 12:01:00 A A1 null
2018-02-03 12:02:00 A A1 null
2018-02-03 12:03:00 A A1 null
2018-02-03 12:04:00 A A2 null
2018-02-03 12:05:00 A A2 null
2018-02-03 12:06:00 B null null
2018-02-03 12:07:00 B null B1
2018-02-03 12:08:00 B null B1
我发现了一个AGGREGATE函数GapFill（） this 使用该功能，我可以从
获取表格select t1.ts, t1.item, t2.infoA, t3.infoB
from
(select ts,gapfill(item) OVER (ORDER BY ts)) t1
LEFT JOIN (select ts,gapfill(infoA) OVER (ORDER BY ts) as infoA) on (t1.ts = t2.ts and t1.item='A') t2
LEFT JOIN (select ts,gapfill(infoB) OVER (ORDER BY ts) as infoB) on (t1.ts = t3.ts and t1.item='B') t3
如果我有很多列，如何简化查询。
答案 0 :(得分：1)
您想要的是@Configuration
public class MyConfig implements ApplicationContextAware {
private ApplicationContext context;
public void setApplicationContext(ApplicationContext context) {
this.context = context;
}
...
}
上的ignore nulls选项。但Postgres（尚未）支持它。
也许最简单的方法是相关子查询：
lag()如果您知道值会单调增加或减少，则可以使用select t.ts,
coalesce(item,
(select t2.item
from t t2
where t2.ts < t.ts and t2.item is not null
order by t2.ts desc
fetch first 1 row only
)
) as item,
coalesce(itemA,
(select t2.itemA
from t t2
where t2.ts < t.ts and t2.itemA is not null
order by t2.ts desc
fetch first 1 row only
)
) as itemA,
coalesce(itemB,
(select t2.itemB
from t t2
where t2.ts < t.ts and t2.itemB is not null
order by t2.ts desc
fetch first 1 row only
)
) as itemB
from t;
或max()。
使用窗口函数的另一种方法使用相同的想法。通过执行累计计数来标识具有相同值的行组。然后将值分散在行上：
min()