Question

I have a result from a query like the below, which does not have a fixed number of columns

ID  COL1    COL2    COL3    COL4
-------------------------------------
1   VAL11   VAL12   VAL13   VAL14
2   VAL21   VAL22   VAL23   VAL24

Now I want the result to be something like this.

RESULT
-----------------------------------------------------
ID:1, COL1:VAL11, COL2:VAL12, COL3:VAL13, COL4:VAL14
ID:2, COL1:VAL21, COL2:VAL22, COL3:VAL23, COL4:VAL24

Please help.

Answer 1

The quick and dirty way, but without the column names and including NULL values:

SELECT tbl::text
FROM   tbl;

The slow & sure way:

SELECT array_to_string(ARRAY[
          'ID:'   || id
         ,'COL1:' || col1
         ,'COL2:' || col2
        ], ', ')  AS result
FROM    tbl;

If a column holds a NULL value, it will be missing in the result. I do not just concatenate, because NULL values would nullify the whole row.
array_to_string() makes sure that commas are only inserted where needed.

---

PostgreSQL 9.1 introduced the new function concat_ws() (much like the one in MySQL) with which we can further simplify:

SELECT concat_ws(', '
          'ID:'   || id
         ,'COL1:' || col1
         ,'COL2:' || col2
        ) AS result
FROM    tbl;