To check if field is NULL use IS NULL, IS NOT NULL operators. MySql reference N.B. I think COALESCE() is SQL standard(-ish), whereas ISNULL() is not.
WHERE your_column '' AND your_column IS NOT NULL it doesn't really add anything (and I personally shun SQL nulls entirely nowadays, so it wouldn't.
SQL IS NULL Clause. NULL is a special value that signifies 'no value'. Comparing a column to NULL using the = operator is undefined. Instead, use WHERE IS.
SQL Server How do you write your query to check for blank (empty) cells? Need to check 3 columns. ColumnA, ColumnB and ColumnC.
Please try: =QUERY('Form Responses 1'!A:N,"SELECT C,E,G,H where G is not null or H is not null order by C,E").
The IS NOT NULL condition is used in SQL to test for a non-NULL value. It returns TRUE if a non-NULL value is found, otherwise it returns FALSE. It can be used.