title: Oracle: column ambiguously defined
body: <p>I know there are lots of questions like these, but my question is not how to get rid of this error but to know how this worked earlier in 9-th version of Oracle.</p>
  
  <p>I've got an old sources written in Ruby and Oracle DB which recently was upgraded to version=11.</p>
  
  <p>I cannot edit data in Oracle DB, only read. so there are two tables lets say: table A(id, name, type, customer) and table B(id,a_id,type,person)</p>
  
  <p>so. there is a query in the source code:</p>
  
  <pre><code>select a.id,b.id from a join b on a.id = b.a_id where type = 'A'
  </code></pre>
  
  <p>so in Oracle 9 this worked perfectly but now i've got "column ambiguously defined" error.</p>
  
  <p>What i'd like to know is:</p>
  
  <pre><code>where type = 'A'
  </code></pre>
  
  <p>is the same as </p>
  
  <pre><code>where a.type = 'A' AND b.type = 'A'
  </code></pre>
  
  <p>or</p>
  
  <pre><code>where a.type = 'A' OR b.type = 'A'
  </code></pre>
  
  <p>?</p>