UNION type mismatch

Question

When I run below query I am getting this error

UNION types text and bigint cannot be matched

SELECT 
    1 AS STEP
  , '' AS ProviderName
  , '' AS Procedurecode
  , Claimid
  , Patient_First_Name
  , Patient_Last_Name
  , DOS
  , SUM(COALESCE(Total_Charge,0))
  , SUM(COALESCE(PaidAmount,0))
  , PostedDate
  , CheckEFTDate
  , CheckEFTNo 
FROM table_name
GROUP BY ProviderName, Claimid, Patient_First_Name, Patient_Last_Name, DOS, PostedDate,
         CheckEFTDate, CheckEFTNo
UNION ALL
SELECT 
    2 AS STEP
  , '' AS ProviderName
  , '' AS Procedurecode
  , COUNT(Claimid)
  , '' AS Patient_First_Name
  , '' AS Patient_Last_Name
  , NULL::date AS DOS
  , SUM(COALESCE(Total_Charge,0))
  , SUM(COALESCE(PaidAmount,0))
  , NULL::date AS PostedDate
  , NULL::date AS CheckEFTDate
  , '' AS CheckEFTNo 
FROM table_name
GROUP BY Claimid

Answer 1

My mistake was is that in union name of columns doesnt matter, but order does matter (maybe I'm wrong, I can't find documentation)

Example:

1) This is fine

select
1 :: integer as someint, 
'1' :: text as sometext

union

select
2 :: integer as someint,
'2' :: text as sometext

returns

someint sometext
1   1   1
2   2   2

2) this is not fine

select
1 :: integer as someint, 
'1' :: text as sometext

union

select
'2' :: text as sometext,
2 :: integer as someint

throws

Error(s), warning(s):

42804: UNION types integer and text cannot be matched

try yourself https://rextester.com/l/postgresql_online_compiler