SQL

t sql null or empty string

select * from vendor
where isnull(vendor_email,'') = ''

sql if empty then

SELECT COALESCE(NULLIF(SomeColumn,''), ReplacementColumn)
FROM SomeTable

sql is null or empty

WHERE ISNULL(column_name);
#Can also use
WHERE column_name IS NULL;
#Example with join
SELECT title FROM series
LEFT JOIN reviews
    ON series.id = reviews.series_id
    WHERE ISNULL(rating);