Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 3)
    ExpressionList (children 2)
     Identifier a
     Identifier b
    TablesInSelectQuery (children 2)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 1)
           ExpressionList (children 2)
            Literal UInt64_1 (alias a)
            Literal UInt64_1 (alias b)
     TablesInSelectQueryElement (children 2)
      TableExpression (children 1)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 1)
           ExpressionList (children 1)
            Literal UInt64_1 (alias a)
      TableJoin (children 1)
       ExpressionList (children 1)
        Identifier a
    Function equals (children 1)
     ExpressionList (children 2)
      Identifier b
      Literal UInt64_0
