concatenation - concatenate four columns that have few Null values in MYSQL

Question

I have four string columns feed1,feed2, feed3, feed4 which have 30 % of NULL values and the requirement is to concatenate four columns with a comma. When I used CONCAT_WS it is giving numbers instead of string values and it is showing ,,, if all the columns are NULL instead of NULL. Please let me know how to do handle the NULL values and concatenate four columns into one column.

Thanks, Madhu

Answer 1

You can use IFNULL function like below,

select CONCAT_WS(',',IFNULL(feed1,'NULL'),IFNULL(feed2,'NULL'),IFNULL(feed3,'NULL'),IFNULL(feed4,'NULL')) as 'value' from TABLE;

To learn more on IFNULL click this.