如何查找数据库中是否存在具有特定值的字段

Question

I am building a application in web but I want to know if is there any way to chech if in a database exist e field with a certain value. So for example I want to check if in table Profile( Profile_Id, User_Id, Address, City...) exist the user with User_Id=20. The reason that I want to check this is that if he user exist I want that when I press the button in my form to update the field of the table Profile and if the user do not exist to insert a new row in the table...

For example:

If( User_Id exist in table Profile(this is the check statement))

$update_query="update Profile...........

else
$update_query=mysql_query("Insert into Profile..............

Please hel me...Thanks in advance

Answer 1

you are looking for

INSERT INTO Profiles (user_id,name,age) VALUES (1,"AL","33")
ON DUPLICATE KEY UPDATE name="Alan", age=34;

Answer 2

The SQL query for this check is:

SELECT 1
FROM   Profile
WHERE  User_Id = ?

You would replace the ? with the value being checked (eg 20). If you use PDO , the replacement can be done using PDOStatement's bindValue method .

If the user exists, a result set of one column will be returned. If not, an empty result set will be returned.