從6個不同的mysql數據庫同步用戶表數據

Question

我有6個mysql數據庫與users_table使用字段email_address相同的表名，現在我想從任何一個數據庫表中缺少的所有6個數據庫中獲得email_address。

請給我一些相同的建議。

Answer 1

這一個選擇一個數據庫中缺少的所有電子郵件，並指出它們存在於哪個數據庫中。

SELECT email, GROUP_CONCAT(db_Name) AS emailIsOnlyIn FROM (
    SELECT 'db1' as db_Name, email FROM db1.yourTable 
    UNION ALL 
    SELECT 'db2' as db_Name, email FROM db2.yourTable 
    UNION ALL 
    SELECT 'db3' as db_Name, email FROM db3.yourTable 
    UNION ALL 
    SELECT 'db4' as db_Name, email FROM db4.yourTable 
    UNION ALL 
    SELECT 'db5' as db_Name, email FROM db5.yourTable 
    UNION ALL 
    SELECT 'db6' as db_Name, email FROM db6.yourTable 
) subquery_alias 
GROUP BY email 
HAVING COUNT(DISTINCT db_name) < 6; 

如果你想知道在哪個數據庫中的郵件丟失這是一個比較複雜一點：

SELECT 
* 
FROM (
    SELECT email FROM db1.yourTable 
    UNION 
    SELECT email FROM db2.yourTable 
    UNION 
    SELECT email FROM db3.yourTable 
    UNION 
    SELECT email FROM db4.yourTable 
    UNION 
    SELECT email FROM db5.yourTable 
    UNION 
    SELECT email FROM db6.yourTable 
) sq, 
    ( SELECT 'db1' as db_Name2 
     UNION ALL 
     SELECT 'db2' as db_Name2 
     UNION ALL 
     SELECT 'db3' as db_Name2 
     UNION ALL 
     SELECT 'db4' as db_Name2 
     UNION ALL 
     SELECT 'db5' as db_Name2 
     UNION ALL 
     SELECT 'db6' as db_Name2 
    )dummy 
WHERE NOT EXISTS (SELECT 1 FROM (
    SELECT 'db1' as db_Name, email FROM db1.yourTable 
    UNION ALL 
    SELECT 'db2' as db_Name, email FROM db2.yourTable 
    UNION ALL 
    SELECT 'db3' as db_Name, email FROM db3.yourTable 
    UNION ALL 
    SELECT 'db4' as db_Name, email FROM db4.yourTable 
    UNION ALL 
    SELECT 'db5' as db_Name, email FROM db5.yourTable 
    UNION ALL 
    SELECT 'db6' as db_Name, email FROM db6.yourTable 
    ) subquery_alias 
WHERE sq.email = subquery_alias.email AND subquery_alias.db_Name = dummy.db_Name2 
) 

• 這裏是一個sqlfiddle這表明概念