SQL 查询某字段不为空

SQL运算符

//不为空
SELECT * FROM `table_name` WHERE 'col'<>''
//为空
SELECT * FROM `table_name` WHERE 'col'=''

SQL命令

//不为空
SELECT * FROM `table_name` WHERE 'col IS NOT NULL
//为空
SELECT * FROM `table_name` WHERE 'col IS NULL