Explain EXPLAIN SYNTAX (children 1)
 SelectWithUnionQuery (children 1)
  ExpressionList (children 1)
   SelectQuery (children 2)
    ExpressionList (children 2)
     Identifier x
     Function if (children 1)
      ExpressionList (children 3)
       Subquery (children 1)
        SelectWithUnionQuery (children 1)
         ExpressionList (children 1)
          SelectQuery (children 1)
           ExpressionList (children 1)
            Function hasColumnInTable (children 1)
             ExpressionList (children 3)
              Function currentDatabase (children 1)
               ExpressionList
              Literal \'test\'
              Literal \'y\'
       Identifier y
       Function concat (children 1)
        ExpressionList (children 2)
         Identifier x
         Literal \'_\'
    TablesInSelectQuery (children 1)
     TablesInSelectQueryElement (children 1)
      TableExpression (children 1)
       TableIdentifier test
