Question

Possible Duplicate:
How to select all records from table apart from the last 100

I wish to run a cron job wiping out some customer information. I have a table which stores the customers information and I am just testing SQL queries to make sure it will work. I am having problems with this:

$result = mysql_query("SELECT * from order-table WHERE order_id NOT IN (
SELECT order_id
from order-table
ORDER BY order_id desc) LIMIT 50");


while($row = mysql_fetch_array($result)){

echo $row['order_id'];

echo "<br />";
}

The problem is that I receive an error: mysql_fetch_array() expects parameter 1 to be resource, boolean given

If I try the query directly in SQL I get a message that LIMIT is not supported in a subquery, so I was hoping someone might be able to help me achieve this in another way? Thank you for your time.

Answer 1

You can’t have LIMIT inside an IN or NOT IN subquery. But you can in a subquery in the FROM or WHERE clause. The trick is to have the subquery return 1 row only and then use < or <= to compare that value.

This will show all rows except the (ordered by order_id) last 50:

SELECT ot.* 
FROM order-table AS ot 
  JOIN 
    ( SELECT order_id
      FROM order-table
      ORDER BY order_id DESC
        LIMIT 1 OFFSET 50
    ) AS lim
    ON ot.order_id <= lim.order_id ;