MySQL で null を置き換える IFNULL() および COALESCE() 関数の詳細な説明

SELECT ISNULL(business_name,'no business_name') AS bus_isnull FROM business WHERE id=2

ネイティブ関数 'isnull' の呼び出しにおけるパラメータ数が正しくありません

SELECT IFNULL(business_name,'no business_name') AS bus_ifnull FROM business WHERE id=2

SELECT IFNULL(business_name,'no business_name') AS bus_ifnull FROM business WHERE id=1

SELECT COALESCE(business_name,'no business_name') AS bus_coalesce FROM business WHERE id=2

SELECT COALESCE(business_name,'no business_name') AS bus_coalesce FROM business WHERE id=1 

COALESCE(business_name,district_id,id) を bus_coalesce として business から id=2 として選択します。 

SELECT * FROM business WHERE ISNULL(business_name)

SELECT * FROM business WHERE business_name IS NULL

SELECT * FROM business WHERE business_name IS NOT NULL