MySQL GROUP_CONCAT() function returns a string result with the comma(,) concatenated non-NULL values from a group

GROUP_CONCAT() function (AKA poor man's window function) returns a string result with the comma(,) concatenated non-NULL values from a group. It returns NULL if there are no non-NULL values.

You can use GROUP_CONCAT() to concatenate multiple MySQL rows into one field.

For the following table i88ca:

id	emailid	email_tagid
509	227776	69
508	227776	74
511	227776	78
512	227776	81
510	227776	84
517	228767	69
516	228767	77
513	228767	79
514	228767	81
515	228767	84

select emailid, group_concat(email_tagid) from i88ca group by emailid;

returns:

emailid	group_concat(email_tagid)
227776	69,74,78,81,84
228767	69,77,79,81,84

More options:

select emailid, group_concat(distinct email_tagid order by email_tagid asc separator ' ') from i88ca group by emailid;

returns:

emailid	group_concat(distinct email_tagid order by email_tagid asc separator ' ')
227776	69 74 78 81 84
228767	69 77 79 81 84