how to prevent insert duplication data in MySQL - php

Question

i have this code that work well.
$sql = "INSERT IGNORE INTO phpc_events (cid, owner, subject, description, ctime)
SELECT '1', '1', title, description, start_tdate from at_courses";
mysql_query($sql);
i put this into this page :
> http://localhost/msigilearnv2/tools/calender/copy_database.php
when first runs the page it will copy table from at_courses to phpc_events..
when second runs.. how i can prevent duplication data? because it keep add same data. i put ignore but still not works

Answer 1

I am sharing you one of the alternative. Lets say you have a record in the database and cid value is '1'.
First step check the value if it is already exists in the database.
$sql = "SELECT cid FROM phpc_events";
$returned = mysql_query($sql);
if(mysql_num_rows($returned) > 0){
while( $row = mysql_fetch_array($returned) ){
$PhpcArray [] = $row; //stores result returned in array to ensure less resource used
}
}
$sqlC = "SELECT anotherId FROM at_courses";
$returnedC = mysql_query($sqlC);
if(mysql_num_rows($returnedC) > 0){
while( $rowC = mysql_fetch_array($returnedC) ){
if( in_array( $rowC['anotherId'], $PhpcArray ) ){
// do nothing as id is already exists in phpc_events
}
else{
// do insertion because id in at_courses is not exist yet in phpc_events
}
}
}
Hope this helps.
Another alternative.
By the way you can also try this query if it matches your column as I don't know how your table structure looks like
SELECT cid
FROM at_courses
WHERE cid NOT IN (
SELECT cid FROM phpc_events
)
This query will return the cid in the at_courses which is not yet occur in phpc_events. Then do the insertion for those cid returned from at_courses table.
Thank you.

Answer 2

My MySQL isn't great, but you will need to do something the like:
$sql = "INSERT IGNORE INTO phpc_events (cid, owner, subject, description, ctime)
SELECT '1', '1', title, description, start_tdate from at_courses"
left join phpc_event on phpc_events.cid = at_courses.cid //(and others you want matched for dups
where phpc_events.cid is null
;

Answer 3

If you have a primary key in your tables, you can replace INSERT with REPLACE. This will insert new records or replace them if the primary key already exists.

Answer 4

alter the table by adding UNIQUE constraint
ALTER TABLE phpc_events ADD CONSTRAINT your_field UNIQUE (cid, owner, subject, description, ctime)