title: What should be the apt joining condition?
body: <p>I have 2 tables of the following format:</p>
  <p>Table 1:</p>
  <pre><code>Id1  Id2   Sent_Email    Date
  123   22     1            24-Oct
  234   11     1            24-Oct
  </code></pre>
  <p>Table 2:</p>
  <pre><code>Id1  Id2   Open_Email    Date
  123   22     1           24 Oct
  123   22     1           24 Oct
  1234  01     1           24 Oct
  </code></pre>
  <p>On left joining table 1 with table 2 on the Id1 and id2
  I am getting:</p>
  <pre><code>Id1  Id2   Open_Email  Sent Email  Date
  123   22     1         1           24 Oct
  123   22     1         1           24 Oct
  </code></pre>
  <p>What change should I make if I only want a single entry in my out for these?
  Desired Output:</p>
  <pre><code>Id1  Id2   Open_Email  Sent Email  Date
  123   22     1         1           24 Oct
  </code></pre>