title: Merge two tables in SQL, with one common column
body: <p>I'm trying to merge to tables in MSSQL, as in the sample below.
  My situation is similiar to this question.
  <a href="https://stackoverflow.com/questions/58447253/t-sql-merging-two-tables-with-common-and-uncommon-columns">T-SQL merging two tables with common and uncommon columns</a></p>
  
  <p>I have tried using the following query:</p>
  
  <pre><code>select coalesce(t1.a, t2.a), t1.b, t1.c, t2.d, t2.k
  from Table1_test t1
  full outer join Table2_test t2 on t2.a = t1.a
  </code></pre>
  
  <p>But it results in this, where the rows that have the same value in column a, merges in the same row</p>
  
  <pre><code>a   b   c      d    k
  1   2   3      5    6
  7   8   9     null  null
  4 null  null   6    7
  9 null  null   0    2
  </code></pre>
  
  <p>Table1_test:</p>
  
  <pre><code>a b c
  1 2 3
  7 8 9 
  </code></pre>
  
  <p>Table2_test:</p>
  
  <pre><code>a d k
  4 6 7
  1 0 2
  </code></pre>
  
  <p>Merged Table I want:</p>
  
  <pre><code>a   b   c      d    k
  1   2   3     null  null
  7   8   9     null  null
  4 null  null   6    7
  1 null  null   0    2
  </code></pre>