MySQL: How to check if Field is NULL or EMPTY

If you want to read out all data records from a table containing an empty string or NULL as value in one specific column, you can use the following query:

SELECT * FROM tab WHERE col IS NULL OR col = ''

With "IS NULL", you can check for NULL, with "= ''", you can check for an empty string.

If you are searching for all datasets where the field is not NULL and not empty, you can use the following query instead:

SELECT * FROM tab WHERE col IS NOT NULL AND col != ''

If you want to use an IF condition for it, you can write it like that, for example:

SELECT IF(col IS NULL OR col = '', 'empty', col) FROM tab

With this query, you are checking at each dataset whether "col" is NULL or empty and depending on the result of this condition, either the string "empty" is returned in the case that the condition is TRUE or the content of the column is returned if not.
2015-06-12 at 18:11

You can also use the IFNULL() function:

1. SELECT IFNULL(1,0); -- returns 1

2. SELECT IFNULL('',1); -- returns ''

3. SELECT IFNULL(NULL,'IFNULL function'); -- returns "IFNULL function"
2019-06-11 at 18:21