Bind an Array to IN-condition

Binding an arbitrary-length array to IN-condition is not simple. You need to create an SQL statement containing a comma-separated list whose length is same with the input data.

Example:

ids = [ ... ] # an arbitrary-length array containing user IDs.

place_holder_string = Array.new(ids.length) {|index| ":id_#{index}"}.join(', ')
# place_holder_string is:
#   ":id_0" if ids.length == 1
#   ":id_0, :id_1" if ids.length == 2
#     ...
cursor = conn.parse("select * from users where id in (#{place_holder_string})")
ids.each_with_index do |id, index|
  cursor.bind_param("id#{index}", id) # bind each element
end
cursor.exec()

However this is awkward. So OCI8.in_cond was added in ruby-oci8 2.2.2. The above code is rewritten as follows:

ids = [ ... ] # an arbitrary-length array containing user IDs.

in_cond = OCI8::in_cond(:id, ids)
cursor = conn.exec("select * from users where id in (#{in_cond.names})", *in_cond.values)

or

ids = [ ... ] # an arbitrary-length array containing user IDs.

in_cond = OCI8::in_cond(:id, ids, Integer) # set the data type explicitly
cursor = conn.exec("select * from users where id in (#{in_cond.names})", *in_cond.values)