MYSQL数据 [英] MYSQL data
问题描述
我正在编写一个控制台应用程序，该应用程序必须根据mysql中的数据生成报告(根据电子邮件列编写报告).我想做的是，用一整列填充数据表.然后，程序应遍历数据表.并将所有电子邮件添加到我在mysql中创建的另一个表中.但是它必须验证它添加的电子邮件不在数据库中.因此，它应该在添加数据之前检查数据库.
请问有人可以帮忙吗?
预先谢谢您.
I am writing a console application which must generate reports according to the data in mysql(write the report according to the email column). What i want to do is, populate a datatable with the one entire column. Then, the program should loop through the datatable. And add every email it comes accross to another table i created in mysql. But it must verify that the email it is adding is not already in the database. So it should check the database before just adding data.
Could i ask anyone for help on this?
Thank you in advance.
推荐答案
您可以在插入记录之前尝试检查特定的记录电子邮件是否已经存在.
You can try before inserting a record for checking whether the specific record-email is already been there or not.
select cout(emailid) where emailid='xyz@abc.com'
or
select * where emailid='xyz@abc.com'
如果检索到的查询结果包含任何行，则您不得插入该电子邮件ID已经存在的记录.
if retrieved query result contains any row then you must not insert the record with that email id as its already present.
另一种方法是:
Another way is to:
SELECT DISTINCT email FROM tablename
这将返回表中电子邮件地址的唯一列表，并避免循环浏览结果.
This will return a unique list of the email addresses in the table and prevent having to loop through results.
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