Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 1)
     QualifiedAsterisk (children 1)
      Identifier t1
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier t1_all (alias t1)
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       TableIdentifier t2_all (alias t2)
      TableJoin (children 1)
       Function equals (children 1)
        ExpressionList (children 2)
         Identifier t1.a
         Identifier t2.a
