从同一个sql表更新带有日期的列
我有这个桌子结构从同一个sql表更新带有日期的列,sql,postgresql,Sql,Postgresql,我有这个桌子结构 id | value ---|---------- 1 | 0.2 2 | 0.3 3 | 0.5 4 | 0.25 5 | 0.37 6 | 0.56 7 | 8 | 9 | 现在我想用元素id=2到5之间的值来更新最后3个元素的值 我这样做是因为听起来很简单 UPDATE table AS z0 SET value = z1.value FROM table as z1 WHERE z1.id BETWEEN 2 AND 5 AN
id | value
---|----------
1 | 0.2
2 | 0.3
3 | 0.5
4 | 0.25
5 | 0.37
6 | 0.56
7 |
8 |
9 |
现在我想用元素id=2到5之间的值来更新最后3个元素的值
我这样做是因为听起来很简单
UPDATE table AS z0
SET value = z1.value
FROM table as z1
WHERE z1.id BETWEEN 2 AND 5
AND z0.id BETWEEn 7 AND 9
但结果是这样的,只取id=2范围内第一个元素的值
id | value
---|----------
1 | 0.2
2 | 0.3
3 | 0.5
4 | 0.25
5 | 0.37
6 | 0.56
7 | 0.3
8 | 0.3
9 | 0.3
这行吗
update table
set value = (select value
from table t2
where id between 2 and 5
order by random()
limit 1
)
where value is null;
唉,尽管我认为应该这样做,但上述方法并不奏效。问题是子查询只执行一次。此版本在以下情况下有效:
correlation子句防止优化只运行一次查询。是演示逻辑的SQL提琴。这行吗
update table
set value = (select value
from table t2
where id between 2 and 5
order by random()
limit 1
)
where value is null;
唉,尽管我认为应该这样做,但上述方法并不奏效。问题是子查询只执行一次。此版本在以下情况下有效:
correlation子句防止优化只运行一次查询。是一个SQL FIDLE,用于演示逻辑。您可以使用它
UPDATE table AS z0
SET value = z1.value
FROM table as z1
WHERE z1.id = (z0.id - 4)
AND z0.id BETWEEn 7 AND 9
你可以用这个
UPDATE table AS z0
SET value = z1.value
FROM table as z1
WHERE z1.id = (z0.id - 4)
AND z0.id BETWEEn 7 AND 9
你想要什么结果?你想要什么结果?是什么阻止子查询返回重复的值?@ClodoaldoNeto。限制1.是什么阻止子查询返回重复值?@ClodoaldoNeto。限制是1。