I have an idea where a user can upload a maximum of 5 images for his or her gallery and can select one of them as his or her profile pic. Is it possible to save the names of all 5 pics in a single column, say, image? Or do I have to make 5 separate columns for storing these file names?
As an example, I could create a column called images and store values in this manner:
{"129cc68678d1e67d18d49d93cec040ce":{"filename":"129cc68678d1e67d18d49d93cec040ce.jpg"},"97ac1e22ea3fd6f02362233d8147ecb5":{"filename":"97ac1e22ea3fd6f02362233d8147ecb5.jpg","primary":true},"eeb239b4edff7e1a09246d38977a5646":{"filename":"eeb239b4edff7e1a09246d38977a5646.jpg"},"55a3810c1b0eaee039c753c12dccbc38":{"filename":"55a3810c1b0eaee039c753c12dccbc38.jpg"}}
Primary:true implies that it's a featured image/ profile picture.
Both of your proposals --- 5 pieces of information in one column and 5 columns --- are bad ideas. What if you ever want to change the limit to 4, or 6, or 20?
Normalize your data instead. Create a table for the images and another for the user-image relationships. In that second table, set a flag for the profile picture.
What you will want to do instead, is create another table to hold your image filenames. Your galleries table would hold an ID and the other info you are storing for the gallery, then your images table would have three columns. One for its ID, one for the filename, and one to store the ID of the gallery it belongs to (called a foreign key).