mysql if 使用

SELECT
    a.uuid AS user_uuid,
    a.user_name,
    a.user_id,

IF (
    c.online_state IS NULL,
    '1',
    c.online_state
) AS online_state,
 e.level_name,
 group_concat(DISTINCT(d.role_name)) AS role_name,
 c.uuid
FROM
    sys_user_role b,
    sys_role d,
    sys_user a
LEFT JOIN biz_document_user_info c ON a.uuid = c.user_id
AND c.sys_status = 1
LEFT JOIN biz_document_level_info e ON c.document_level_id = e.uuid
AND e.sys_status = 1
WHERE
    a.uuid = b.user_uuid
AND b.role_uuid = d.uuid
AND a.sys_status = 1
AND b.sys_status = 1
AND b.role_uuid IN (
    'qhyf1011',
    'qhyf1010',
    'qhyf1040',
    'qhyf1046'
)
AND a.user_name LIKE '%王玉花%'
AND (c.online_state = '1' OR c.online_state IS NULL)
GROUP BY
    a.user_id,
    online_state
ORDER BY
    user_uuid ASC