Explain EXPLAIN QUERY TREE (children 2)
 Set
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 4)
    ExpressionList (children 1)
     Function count (children 1)
      ExpressionList
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier x
    Function or (children 1)
     ExpressionList (children 3)
      Function and (children 1)
       ExpressionList (children 2)
        Identifier A
        Identifier B
      Function and (children 1)
       ExpressionList (children 3)
        Identifier A
        Identifier B
        Identifier C
      Function and (children 1)
       ExpressionList (children 2)
        Identifier B
        Identifier C
    Set
