是否可以使用Rails 4查询postgres数组的特定索引？

Question

With a database column migrated like this:

add_column :documents, :array_column, :string, array: true

I understand it's possible to do this to query any element of the array:

Document.where("'foo' = ANY (array_column)")

My question is whether or not I can specifically query the second (or any other single) element of an array?

Answer 1

You can use the usual array indexing notation but remember that SQL arrays are 1-based rather than 0-based:

Document.where("array_column[2] = 'foo'")

The fine manual has more on accessing arrays .