Split comma separated column data into additional columns

Exploring other flavors

Time to explore some more exotic dishes in our SQL kitchen!

Meet split_part() from PostgreSQL

PostgreSQL offers the split_part() function, which slices apart a string based on a delimiter and returns the nth substring:

SELECT
  split_part(YourColumn, ',', 1) AS col1,  -- Fishing the first fish out of my comma sea
  split_part(YourColumn, ',', 2) AS col2,  -- Surfing to the second island in the comma ocean
  ...
FROM YourTable;  


But beware, prying for an nth substring in an empty string returns an empty string. Be cautious of the submarine traps in our comma sea!

array-fying columns with string_to_array()

PostgreSQL provides a nifty function, string_to_array, which saves you from hard-coding positions:

SELECT
  string_to_array(YourColumn, ',')[1] AS col1,  -- Getting the first sip of comma soup
  string_to_array(YourColumn, ',')[2] AS col2,  -- Diving for the second pearl in the comma oyster
  ...
FROM YourTable;  


‘CSV in a column?’, the SQL puritans gasp in horror. Yes, it’s not the best practice. Consider a schema redesign to normalize this data, or else face the wrath of maintainability demons.

DIY functions

Wrap up all of your logic into a custom function for later use:

CREATE FUNCTION split_csv (input_string text, delimiter text, part_number integer)
RETURNS text AS $$
BEGIN
  RETURN split_part(input_string, delimiter, part_number);  -- My precious function does my dirty work!
END;
$$ LANGUAGE plpgsql IMMUTABLE;

-- Usage
SELECT split_csv(YourColumn, ',', 1) FROM YourTable;


DIY functions – a snazzy way to keep your code clean and handsome!

Awareness of performance

Performance is a beast that waits around the corner. Be aware. Heavy usage of split methods could lead to performance downfall. Always test these methods against large data sets and may all the odds be in your favor!

Possible pitfalls

Happy encounters with empty strings

When splitting strings, empty strings might tag along, especially with irregular CSV columns. Be ready for this cheeky encounter!

Array manipulation tools to the rescue

regexp_split_to_array is useful when delimiters are tricky:

SELECT
  (regexp_split_to_array(YourColumn, ', *'))[1] AS col1,  -- Sweeping for the first comma dust
  (regexp_split_to_array(YourColumn, ', *'))[2] AS col2   -- Shaking the second comma tree 
FROM YourTable;  


Remember, a comma followed by spaces can be a wee bit tricky. Stay vigilant!

Performance side-effects

While functions like regexp_split_to_array are power tools, they might come at the expense of performance. As they say, with great power, comes great responsibility!