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    <p>Unfortunately, I've determined it's not possible to do it without using <code>execute</code>.</p> <h2>Why it doesn't work</h2> <p>By examining the ActiveRecord source, we can find the code for <code>create_table</code>:</p> <p>In <a href="http://github.com/rails/rails/blob/5a7d31913bb16977ec85d55de34ac0d79b512d62/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb#L161" rel="nofollow noreferrer"><code>schema_statements.rb</code></a>:</p> <pre><code>def create_table(table_name, options={}) ... table_definition.primary_key(options[:primary_key] || Base.get_primary_key(table_name.to_s.singularize)) unless options[:id] == false ... end </code></pre> <p>So we can see that when you try to specify a primary key in the <code>create_table</code> options, it creates a primary key with that specified name (or, if none is specified, <code>id</code>). It does this by calling the same method you can use inside a table definition block: <code>primary_key</code>.</p> <p>In <a href="https://github.com/rails/rails/blob/a63f7a136401b59db52fb802180f6c9793d83bc2/activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb#L89" rel="nofollow noreferrer"><code>schema_statements.rb</code></a>:</p> <pre><code>def primary_key(name) column(name, :primary_key) end </code></pre> <p>This just creates a column with the specified name of type <code>:primary_key</code>. This is set to the following in the standard database adapters:</p> <pre><code>PostgreSQL: "serial primary key" MySQL: "int(11) DEFAULT NULL auto_increment PRIMARY KEY" SQLite: "INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL" </code></pre> <h2>The workaround</h2> <p>Since we're stuck with these as the primary key types, we have to use <code>execute</code> to create a primary key that is not an integer (PostgreSQL's <code>serial</code> is an integer using a sequence):</p> <pre><code>create_table :employees, {:id =&gt; false} do |t| t.string :emp_id t.string :first_name t.string :last_name end execute "ALTER TABLE employees ADD PRIMARY KEY (emp_id);" </code></pre> <p>And as <a href="https://stackoverflow.com/questions/1200568/using-rails-how-can-i-set-my-primary-key-to-not-be-an-integer-typed-column/1429146#1429146">Sean McCleary mentioned</a>, your ActiveRecord model should set the primary key using <code>set_primary_key</code>:</p> <pre><code>class Employee &lt; ActiveRecord::Base set_primary_key :emp_id ... end </code></pre>
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    1. POUsing Rails, how can I set my primary key to not be an integer-typed column?
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    1. USRudd Zwolinski
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    1. COthe workaround will make the rake db:test:clone or rake db:schema:load to create emp_id as integer column.
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      1. USDonny Kurnia
    2. COactually, now you should be using `self.primary_key=` instead of `set_primary_key`, since the latter is deprecated.
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      1. USGary S. Weaver
 

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