如何在Rails Rake任务中将参数传递给mysql查询？

Question

I am changing the encoding of all my tables from latin1 to utf8mb4 using a rails rake task.

I want to:

1. Grab all the tables where the encoding is NOT utf8mb4
2. Change the character set for each of those tables.

I can grab all the tables that have the wrong enconding with

results = ActiveRecord::Base.connection.execute <<-STRING
   SHOW TABLE STATUS WHERE collation <> 'utf8mb4'
STRING

I'm stuck with how to pass the table name for each of those tables to the mysql query so that the table encoding can be altered.

results.each do |table|
  ActiveRecord::Base.connection.execute <<-STRING
  ALTER TABLE #{table.table_name} CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin
  STRING
end

Answer 1

Each result is an array:

results.first.class
 => Array

And the first value returned by SHOW TABLE STATUS is the table name. So you should be able to use something like:

results.each do |table|
  ActiveRecord::Base.connection.execute <<-STRING
  ALTER TABLE #{table[0]} CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_bin
  STRING
end