Mysql group_concat adds a separator for empty fields

Question

There is a sample schema in here: http://sqlfiddle.com/#!2/c0723a/2

query is select id,group_concat(val) from test group by id

result is

ID GROUP_CONCAT(VAL)
1 ,64,66,,203,214,204

I wanted to concat val field without a comma for empty records like this

ID GROUP_CONCAT(VAL)
1 64,66,203,214,204

Answer 1

Simply use Replace

select id,replace(group_concat(val),',,',',') from test group by id

Or you can use IF

select id,group_concat(if(val ='',null, val)) from test group by id

Or You can use NULLIF

select id,group_concat(Nullif(val,'')) from test group by id

Fiddle Demo

Answer 2

SELECT id, GROUP_CONCAT(val) FROM test 
WHERE val is not null AND val <> '' 
GROUP BY id

Answer 3

Add an IF check, GROUP_CONCAT will skip the NULL value.

select id, group_concat(IF(val = '', null, val)) from test group by id

THE SQLFIDDLE.