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Asked: 2026-06-17T08:19:30+00:00

I’d like to change an existing MySQL column from VARCHAR to VARCHAR BINARY in

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I’d like to change an existing MySQL column from VARCHAR to VARCHAR BINARY in order to change it to be case-sensitive (see: https://stackoverflow.com/a/3396315/93995)

What’s the proper migration syntax for this? I tried

change_column :my_table, :my_column, :binary, :limit => 255

but that tries to change it to a blob(255). Also complains:

Mysql2::Error: BLOB/TEXT column 'my_column' used in key specification without a key length:   ALTER TABLE `my_table` CHANGE `my_column` `my_column` blob(255) DEFAULT NULL
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1 Answer

  1. Editorial Team

    To change a single column to be case sensitive, you’ll need to use SQL DDL directly to change to the collation to ‘utf8_bin’:

    def up
 execute("ALTER TABLE my_table MODIFY `my_column` varchar(255) CHARACTER SET utf8 COLLATE utf8_bin;")
end

    Note that this is still using the ‘varchar’ type as storage, only the collation (interpreted meaning) is defined as ‘binary’ for comparison purposes. Also note that you may not be able to compare columns with different collations, so make sure this is what you really want.

    If you wanted to make a whole table use a specific collation, that can easily be done:

    create_table :my_table, :options => 'ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_bin' do |t|
  t.string :my_column
  t.string :my_other_column
end
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