SelectWithUnionQuery (children 1)
 ExpressionList (children 1)
  SelectQuery (children 1)
   ExpressionList (children 2)
    Function toDecimal64 (children 1)
     ExpressionList (children 2)
      Literal Float64_123456789012345.12
      Literal UInt64_4
    Function JSONExtract (children 1)
     ExpressionList (children 3)
      Literal \'{"a":123456789012345.12}\'
      Literal \'a\'
      Literal \'Decimal(30, 4)\'