How to get initials easily out of text field using Postgres - sql

Question

I am using Postgres version 9.4 and I have a full_name field in a table.
In some cases, I want to put initials instead of the full_name of the person in my table.
Something like:
Name | Initials
------------------------
Joe Blow | J. B.
Phil Smith | P. S.
The full_name field is a string value (obviously) and I think the best way to go about this is to split the string into an array foreach space i.e.:
select full_name, string_to_array(full_name,' ') initials
from my_table
This produces the following result-set:
Eric A. Korver;{Eric,A.,Korver}
Ignacio Bueno;{Ignacio,Bueno}
Igmar Mendoza;{Igmar,Mendoza}
Now, the only thing I am missing is how to loop through each array element and pull the 1st character out of it. I will end up using substring() to get the initial character of each element - however I am just stuck on how to loop through them on-the-fly..
Anybody have a simple way to go about this?

Answer 1

Use unnest with string_agg:
select full_name, string_agg(substr(initials, 1,1)||'.', ' ') initials
from (
select full_name, unnest(string_to_array(full_name,' ')) initials
from my_table
) sub
group by 1;
full_name | initials
------------------------+-------------
Phil Smith | P. S.
Joe Blow | J. B.
Jose Maria Allan Pride | J. M. A. P.
Eric A. Korver | E. A. K.
(4 rows)
In Postgres 14+ you can replace unnest(string_to_array(...)) with string_to_table(...).
Test it in db<>fiddle.

Answer 2

You can also create a helper function for this, in case you want to use similar logic in multiple queries. Check this out
--
-- Function to extract a person's initials from the full name.
--
DROP FUNCTION IF EXISTS get_name_initials(TEXT);
CREATE OR REPLACE FUNCTION get_name_initials(full_name TEXT)
RETURNS TEXT AS $$
DECLARE
result TEXT :='';
part VARCHAR :='';
BEGIN
FOREACH part IN ARRAY string_to_array($1, ' ') LOOP
result := result || substr(part, 1, 1) || '.';
END LOOP;
RETURN result;
END;
$$ LANGUAGE plpgsql;
Now you can simply use this function to get the initials like this.
SELECT full_name, get_name_initials(full_name) as initials
FROM my_table;
SELECT get_name_initials('Phil Smith'); -- Returns P. H.
SELECT get_name_initials('Joe Blow'); -- Returns J. B.

Answer 3

SqlFiddleDemo
WITH add_id AS (
SELECT n.*, row_number() OVER (ORDER BY "Name") AS id
FROM names n
),
split_names AS (
SELECT id, regexp_split_to_table("Name", E'\\s+') AS single_name
FROM add_id
),
initials AS (
SELECT id, left(single_name, 1) || '.' AS initial
FROM split_names
),
final AS (
SELECT id, string_agg(initial, ' ')
FROM initials
GROUP BY id
)
SELECT a.*, f.*
FROM add_id a
JOIN final f USING (id)
For debug I create the Initial to Show how match the string_agg
| Name | Initials | id | id | string_agg |
|----------------|----------|----|----|------------|
| Eric A. Korver | E. A. K. | 1 | 1 | E. A. K. |
| Igmar Mendoza | I. M. | 2 | 2 | I. M. |
| Ignacio Bueno | I. B. | 3 | 3 | I. B. |
| Joe Blow | J. B. | 4 | 4 | J. B. |
| Phil Smith | P. S. | 5 | 5 | P. S. |
After some work I got a compact version SqlFiddleDemo
SELECT "Name", string_agg(left(single_name, 1) || '.', '') AS Initials
FROM (
SELECT
"Name",
regexp_split_to_table("Name", E'\\s+') AS single_name
FROM names
) split_names
GROUP BY "Name"
OUTPUT
| Name | initials |
|----------------|----------|
| Eric A. Korver | E.K.A. |
| Igmar Mendoza | M.I. |
| Ignacio Bueno | I.B. |
| Joe Blow | B.J. |
| Phil Smith | P.S. |