Check for duplicates before inserting

Question

Before inserting into the database, I\'m using the following code to check for duplicates. To me, a duplicate is only considered a duplicate when name, de

Answer 1

You can still run into race conditions where 2 users try to insert dups at the same time, checking for dups using a select statement simultaneously gives both users the go ahead to insert their records. I prefer to set unique index on the DB and then catch the error that bubbles up from the DB.

Answer 2

You want to do the following:

$dupesql = "SELECT * FROM table where (name = '$name' AND description = '$description' AND manufacturer = '$manufacturer' AND city ='$city' AND price = '$price' AND enddate = '$end_date')";

$duperaw = mysql_query($dupesql);

if (mysql_num_rows($duperaw) > 0) {
  //your code ...
}

See Here for more information.

Answer 3

As I see it your question can be broken down into 2 parts. Why is my PHP code not working? I don't know, don't know much PHP and other people seem to have just answered that :-). The second question is how can I check for duplicates? You're checking for duplicates the completely wrong way.

Create a unique index / primary key on your table. Then when you try to insert the DB will throw an error if there's a duplicate. Catch the error and deal with it how you want. Counting the number of records is definitely the wrong way to go and will be a significant detriment to the speed of your code.

Answer 4

Try Following

  INSERT IGNORE INTO person_tbl (last_name, first_name) 
  -> VALUES( 'Jay', 'Thomas');

Answer 5

Try this one:

foreach($states_to_add as $item) {
    $dupesql = "SELECT 
                    name 
                FROM 
                    table 
                WHERE 
                    (name = '$name' 
                        AND description = '$description' 
                        AND manufacturer = '$manufacturer' 
                        AND city ='$city'
                        AND price = '$price' 
                        AND enddate = '$end_date'
                    )";

    $duperaw = mysql_query($dupesql);

    if( mysql_num_rows($duperaw) ) {
        echo nl2br("$name already exists in $city \n");
    } 
    else {
        $sql = "INSERT INTO table (..... (here go the values to be inserted)

Answer 6

You don't need to check for uniqueness in PHP, you can just do the whole test in MySQL:

INSERT INTO table1 (name, description, ......)
  SELECT name1, description1, manufacturer1, city1, price1, enddate1
  FROM (SELECT * FROM ( 
    SELECT 
      @name:= '$name' as name1
      ,@description:= '$description' as description1
      ,.....
    FROM DUAL as d1
    LEFT JOIN table1 t1 
           ON (t1.name = d1.name1 
          AND t1.description = d1.description1
          AND ......)
    WHERE t1.name IS NULL) s1) s2

This will only insert the values if they pass the uniqueness test.