复杂的sql语句join的使用（left join,right join）

SELECT u.*,count(u.id) AS sum
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                    FROM user AS u
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                    LEFT JOIN post AS p
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                    ON p.user_id = u.id
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                    RIGHT JOIN user_has_group as up
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                    ON up.user_id = u.id
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                    RIGHT JOIN user_has_email as ue
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                    ON ue.user_id = u.id
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                    WHERE u.username != ''
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                    AND up.group_id = {$args['groupid']}
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                    AND ue.email = '{$args['useremail']}'
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                    GROUP BY u.id ORDER BY u.id desc