Rails 4 如何找到字符串列的最大长度

Question

To find the maximum length of string column in SQL is:

select max(length(<column>)) from <table>

Can anyone show how to do the same in Rails 4 activerecord or even squeel?

Answer 1

您可以使用Model.pluck("max(length(column))") ，它不会将所有内容加载到内存中。

Answer 2

Something like this?

Model.pluck(:column).max_by(&:length)

#=> will return the longest string

Another option would be to just execute a query in SQL:

Model.connection.execute("SELECT MAX(LENGTH(column)) FROM my_table")