Postgresql 用随机值更新每一行
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Postgresql update each row with a random value
提问by dreamriver
This is similar to other questions but it appears to vary on a database-by-database implementation. I am using postgres and things like NEWIDdo not appear to exist.
这与其他问题类似，但它似乎因逐个数据库的实现而异。我正在使用 postgres 和类似的东西似乎NEWID不存在。
This is what I want to work:
这就是我想要的工作：
update foo set bar = (select floor(random() * 10) + 1);
I understand whyit doesn't but I can't seem to find a suitable solution that works for Postgres. I want the value of barto be a random number between 1 and 10 that differs perrow.
我明白为什么没有，但我似乎无法找到适用于 Postgres 的合适解决方案。我希望 的值是bar1 到 10 之间的随机数，每行不同。
回答by Gordon Linoff
I think that Postgres might optimize the subquery. Doesn't this work?
我认为 Postgres 可能会优化子查询。这不行吗？
update foo
set bar = floor(random() * 9 + 1); -- from 1 to 10, inclusive
回答by Alexey Khivin
For PostgreSQL (tested on 9.5) this can be solved by adding fake "where" clause
对于 PostgreSQL（在 9.5 上测试），这可以通过添加假“where”子句来解决
update foo set bar = (select floor(random() * 10) + 1 where foo.id = foo.id);
