MySQL的：交易？ 插入和更新

Question

I need to do 2 query.

Basically it's a

mysql_query("INSERT INTO table ($value1,$value2)");

and

mysql_query("UPDATE table2 SET field1 = '$value1', field2 = '$value2'");

I think I can simply do a

if (mysql_query("INSERT ...") !== false) {
   mysql_query("UPDATE ...");
}

In this case should I use a transaction? And how should I use it?
Or can i leave that simple if?

Thanks

Answer 1

You will generally use transactions if you want some "all or nothing" behavior.

Basically, with transactions, you can :

• Start a transaction
• Do the first query
• If it succeeds, do the second query
  • If it succeed, commit the transaction
  • Else, rollback the transaction -- cancelling both queries that correspond to that transaction.

If working with mysql_* function, you'll have to :

• Start the transaction, with a START TRANSACTION query
• Do your queries
• Depending on the result of those queries, either do a COMMIT or a ROLLBACK query.

To detect whether a query succeeded or not, you can indeed check the return value of mysql_query() : it will return false in case of an error.

Note : MySQL is the old extension -- and doesn't have functions to deal with transactions ; which means you have to deal with them as regular queries.

Working with MySQLi , you could use :

• mysqli::autocommit() to disable autocommit
• and mysqli::commit() or mysqli::rollback()

Answer 2

For insert and updates MySQL has a good, alternative solution - "ON DUPLICATE KEY UPDATE". It does what you want safely in a single query:

INSERT .... ON DUPLICATE KEY UPDATE

(also the key must be set as unique in this scenario)

http://dev.mysql.com/doc/refman/5.0/en/insert-on-duplicate.html