如何獲取所有記錄，即使那些沒有匹配的連接 - MySQL

Question

我有以下SQL獲取所有客戶記錄，然後找到該客戶的匹配文檔（points_audit_customers.id = points_audit_documents._audit_id），但它的工作原理它跳過所有沒有文件匹配的客戶，原本很好，但現在規範已經改變，我需要所有的客戶來，如果沒有找到文件，仍然顯示客戶的詳細信息，但離開文件字段sql爲零或null。

這可能嗎？我想知道是否可以使用CASE嗎？我想如果這是不可能的，我可以修改SQL來只選擇客戶的詳細信息，然後在PHP循環中選擇匹配的文檔，理想情況下，如果可以的話，我寧願用SQL語句來完成。

三江源

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 

Answer 1

您需要使用outer join：

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 

Answer 2

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