MySQL condition

Question

I'm still pretty new with MySQL and I don't know the best way to do this.

I have a table with incremented values, and if the values exceed a certain limit, I'd like to know. So lets say I have this table with a current column and capacity column. A row in current is incremented by user input and I want to know when the value in a current row exceeds or meets its corresponding capacity.

If current is still below the capacity, I would like the query to return true. However, if current meets or exceeds capacity, I would like the query to return false.

Thanks!

knittl · Accepted Answer · 2010-07-29 09:24:18Z

4

in mysql that's easy:

select (current >= capacity) as exceeded from table

edited Jul 29, 2010 at 9:24

answered Jul 29, 2010 at 8:43

knittl

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3 Comments

Mark Baker Over a year ago

Is => a valid operator in MySQL now, or did you mean >= ?

BoltClock Over a year ago

Shouldn't this return true only when current < capacity?

tau Over a year ago

Thank you for the replies. I'm actually using UPDATE on the row. How would I apply this to an UPDATE query? Thanks!

BoltClock · Accepted Answer · 2010-07-29 17:05:02Z

2

Add a WHERE clause to do that check in your UPDATE query:

// I assume you mean you want to increment the current column by 1,
// but it's your table so change the SET values as needed
$updated = mysql_query('UPDATE table SET current = current + 1 WHERE id = ' . intval($row_id) . ' AND current < capacity');

Then check mysql_affected_rows() of the UPDATE query:

if (mysql_affected_rows() > 0)
{
    // Success
}

edited Jul 29, 2010 at 17:05

answered Jul 29, 2010 at 9:38

BoltClock

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2 Comments

tau Over a year ago

Thanks! This is just what I needed. I have one question, though. Whenever I put the variable associated with my mysql_query in mysql_affected_rows, it wouldn't work (says it wasn't valid MySQL resource). When I removed it and used mysql_affected_rows() without an argument, it worked! Do you know why?? Thanks!

BoltClock Over a year ago

Because it was a mistake on my part: the variable isn't supposed to be there. I've edited my answer to remove it. Sorry for the confusion! Glad my solution worked for you though :)

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