PHP-SQL-内部联接不起作用

Question

I have 3 tables in the database

first-table-name : savedemail

ID    email
================
1     user.com
2     xy.com
3     user2.com

second-table-name : volley

mac        email
===================
12345     hhhhh.com
22222     user2.com
33333     ggggg.com

third-table-name : macadd

 mac
=========
00000
00000
22222

what I am trying to do is compare each row of email of savedemail table to the each row of email of volley table . if the email matches then I want to store mac of volley to mac of macadd table if it already not exists.

the my code below is not inserting anything to table also no errors\\warnings

Here is query I am using

SELECT savedemail.email , volley.mac , volley.email
FROM savedemail
INNER JOIN volley
ON savedemail.email=volley.email
WHERE savedemail.email=volley.email REPLACE macadd (mac)
VALUES ('volley.mac')

Answer 1

Try this query instead:

INSERT INTO macadd (mac)
SELECT volley.mac 
FROM volley 
WHERE volley.email = (
    SELECT email 
    FROM savedemail 
    WHERE email = volley.email
    AND (
        SELECT count(mac) FROM macadd WHERE macadd.mac = volley.mac
    ) = 0
)

A little difficult to put into words, I'm sure you get the gist of it, but mostly you would select all the emails from savedemail's where the email value from that table matches one from the volley table, and so long as that mac doesn't exist in the macadd table, append that mac to the macadd table.

Disclaimer: My MySQL knowledge is somewhat limited, so I can almost certainly assure you there are quicker/less-resource-intensive ways to do this; however, the above method does work in my testing.

Answer 2

Here's one option using the outer join / null check approach:

insert into macadd
select v.mac
from savedemail s 
    join volley v on s.email = v.email
    left join macadd m on v.mac = m.mac
where m.mac is null

• SQL Fiddle Demo

---

Alternatively you can use not exists , but from my experience with mysql queries, the outer join / null check will generally outperform it.

insert into macadd
select v.mac
from savedemail s 
    join volley v on s.email = v.email
where not exists (
    select 1
    from macadd 
    where mac = v.mac
)

• More Fiddle