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我有以下 SQL，它正在获取所有客户记录，然后找到该客户的匹配文档（points_audit_customers.id = points_audit_documents._audit_id）并且它可以工作，但是它正在跳过所有没有要匹配的文档的客户本来很好，但现在规范已经改变，但我需要所有客户都来，如果没有找到文档，那么仍然显示客户详细信息，但将 sql 中的文档字段保留为零或空。

这可能吗？我想知道是否可以以某种方式使用 CASE？我想如果不可能的话，我可以修改 SQL 以仅选择客户详细信息，然后在 PHP 循环中选择匹配的文档，如果可以的话，理想情况下我更愿意使用 SQL 语句。

谢谢

SELECT points_audit_customers.*, points_audit_documents.branch,
SUM(points_audit_documents.amount_invoiced) AS the_amount_invoiced,
SUM(points_audit_documents.amount_spent) AS the_amount_spent,    
SUM(points_audit_documents.points_invoiced) as invoiced_points,  
SUM(points_audit_documents.points_spent) as spent_points,
SUM(points_audit_documents.points_bonus) as bonus_points
FROM points_audit_customers, points_audit_documents
WHERE import_month = '$import_month'
AND points_audit_customers.id = points_audit_documents.audit_id
AND processed = 1
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2 回答 2

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您需要使用外部联接：

FROM  points_audit_customers LEFT JOIN points_audit_documents
        ON points_audit_customers.id = points_audit_documents.audit_id
WHERE import_month = '$import_month'
  AND processed = 1  -- if this is in documents table, move to the join criteria
于 2013-04-29T23:00:40.443 回答
0 
SELECT pac.*, pad.branch,
    IFNULL(SUM(pad.amount_invoiced), 0) AS the_amount_invoiced,
    IFNULL(SUM(pad.amount_spent), 0)    AS the_amount_spent,    
    IFNULL(SUM(pad.points_invoiced), 0) AS invoiced_points,  
    IFNULL(SUM(pad.points_spent), 0)    AS spent_points,
    IFNULL(SUM(pad.points_bonus), 0)    AS bonus_points
FROM points_audit_customers pac 
LEFT JOIN points_audit_documents pad ON ( pad.id = pac.audit_id )
WHERE processed = 1
    AND import_month = '$import_month'
GROUP BY pac.id
于 2013-04-29T23:08:25.867 回答