title: populate many to many table from existing tables
body: <p>I have two existing tables with data populated</p>
  
  <p>table A 
  --tableA_id
  --contentA</p>
  
  <p>table B
  --tableB_id
  --contentB</p>
  
  <p>Now, I want to create a many to many relationship table </p>
  
  <p>table A_B
  --tableA_id
  --tableB_id</p>
  
  <p>the question is that how to write a sql script (I am new to sql) to populate table A_B using the existing data from table A and table B. Many thanks,</p>
  
  <p>Mark</p>