Writing to mysql databse PHP. How to update value in field??

Question

I have a field in my mysql table that I want to update.

Example: In my database the field amount has a value of 4 and I want to add 6 to the value.

How would I add 6 to the existing value???

This is what I have so far but this just deletes the existing value and adds a new one:

mysql_send("UPDATE peopletable SET amount='$amount' WHERE id='100' ");

Answer 1

You can do this to add something to a supplied value:

UPDATE peopletable SET amount='$amount' + 6 WHERE id='100'

To update the existing value, do:

UPDATE peopletable SET amount = ammoutn  + 6 WHERE id='100'

Answer 2

UPDATE peopletable SET amount = amount + 6 WHERE id = 100

Answer 3

UPDATE peopletable SET amount=amount+6 WHERE id='100'

or if $amount is the value that you're adding (6 isn't static)

   " UPDATE peopletable SET amount=amount+$amount WHERE id='100'"

Answer 4

mysql_send("UPDATE peopletable SET amount=`amount`+6 WHERE id='100' ");

Answer 5

UPDATE peopletable SET amount=amount + 6 WHERE id='100'

or

UPDATE peopletable SET amount+= 6 WHERE id='100'

Answer 6

Please make sure that you are sanitising your input and $amount is numeric.

Here's what your query should look like:

mysql_send("UPDATE peopletable SET amount+=$amount WHERE id='100' ");

This will take the original value and add $amount to it.