复杂的sql语句join的使用（left join,right join）_MySQL

bitsCN.com 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 bitsCN.com