选择VARCHAR列的最大值-MySQL

Question

My table for message inbox concept email is a primary in the table. I want to get the last message which is sent by particular email.

tbl_msg:

id
email
msg

Example Data:

Id  email            msg
1   xyz@gmail.com    This is test    
2   abc@gmail.com    All is well
3   xyz@gmail.com    This is test2

I want to get the last appearance of each email and msg

Id  email            msg

2   abc@gmail.com    All is well
3   xyz@gmail.com    This is test2

What I tried:

SELECT cnote.`id`,cnote.`email`,cnote.`msg` FROM `tbl_msg` cnote inner join (select distinct email,id from client_com group by email) as note
on cnote.id=note.id

Guide me if I wrong

Answer 1

To get the latest messsage for each email address in the table you do not need a JOIN , you just need to ORDER and GROUP BY :

SELECT `id`, `email`, `msg`
FROM `tbl_msg`
GROUP BY `email`
ORDER BY `id` DESC

Answer 2

Use This query:

SELECT m1.* FROM tbl_msgs m1 LEFT JOIN tbl_msgs m2  ON (m1.email = m2.email AND m1.id < m2.id) WHERE m2.id IS NULL;

This will join with the same table and with condition m1.id < m2.id , will get the latest one.

Another option is using subquery:

SELECT * FROM tbl_msgs WHERE id IN (SELECT MAX(id) FROM tbl_msgs GROUP BY email);

Answer 3

You can use this query:

SELECT id, email, msg FROM you_table 
GROUP BY email
ORDER BY id DESC

With this one you will have only 1 row per email, and you'll have the last because is ordered by id DESC.

Answer 4

If you are running a PDO connection (The way I know to do it, not sure if there is a MySQLi way)

$theLastIdGiven = $handlerDbConnection->lastInsertId();

Or if you want to run it through a query, and get the last result, just add ORDER BY id DESC LIMIT 0, 1 and that will order the data by id in a descending form then get the first bit of data :)

Hope this helped you!

Answer 5

选择ID，电子邮件，来自tbl_msg的消息在哪里输入ID（（从tbl_msg GROUP BY电子邮件中选择MAX（ID））