Turning a column of values into a single comma-separated line, or the reverse, is a one-line job in code and a fiddly one by hand once quoting and escaping get involved. This converts a column of lines into a comma-separated list, or splits a delimited list back into one item per line.
When you'd use this
Building a SQL `IN (...)` clause from a pasted list of IDs, turning a column copied from a spreadsheet into a comma-separated value for a config file or API parameter, or splitting a long comma-separated string back into a readable list.
Common errors
A value that contains a comma of its own needs quoting to survive the round trip without being split in the wrong place. If a converted list appears to have gained items it shouldn't have, look for unquoted commas inside the original values.
Frequently asked questions
Can I use a delimiter other than a comma?
Yes. Semicolons, pipes, tabs and other delimiters are common alternatives, and they help specifically when the data itself might contain commas and a different separator removes the ambiguity.