How to md5 all columns regardless of type

Question

I would like to create a sql query (or plpgsql) that will md5() all given rows regardless of type. However, below, if one is null then the hash is null:

UPDATE t         


        

Answer 1

Have you tried using CONCAT()? I just tried in my PG 9.1 install:

SELECT CONCAT('aaaa',1111,'bbbb');     => aaaa1111bbbb
SELECT CONCAT('aaaa',null,'bbbb');     => aaaabbbb

Therefore, you can try:

SELECT MD5(CONCAT(column1, column2, column3, column_n))    => md5_hash string here