如果mysql表包含data，请更新它，如果不插入数据（PHP）

Question

i'm new to php . i'm just wondering which PHP script can detects if a MySQL database's table contains data . If yes , it will update the data with the submitted form data. If not(blank) it will insert the form data into it.

I know how to insert data using php just wondering how can i CHECK if data exist in a table.

Thanks and have a nice day .

Answer 1

You are looking for INSERT ... ON DUPLICATE KEY UPDATE .

INSERT INTO table (a,b,c) VALUES (1,2,3)
  ON DUPLICATE KEY UPDATE c=c+1;

Just append the ON DUPLICATE KEY UPDATE x=y, z=a to your current INSERT and if the unique value you try to insert already exists, the row containing it is updated.

Answer 2

MySQL可以根据您的检查方式（主键？）提供帮助-参见http://www.xaprb.com/blog/2006/02/21/flexible-insert-and-update-in-mysql/

Answer 3

Checking if data exists in a database is a read operation, so you'd use a SELECT statement. If the SELECT statement returns a non-empty recordset, then you know the data exists. Bonus: you also know the id number of the data you're looking for, for use in your update operation.

The INSERT... ON DUPLICATE KEY UPDATE is great if you know the unique id number of the row you're updating... which you might now.

The only issue with using a SELECT statement is that the operation is not guaranteed to be atomic - that is, this might happen:
- you run the SQL statement and get an empty set
- a different process inserts that form data into the database
- the first process, that ran the select statement, inserts the same form data

Good luck!