The MySQL SQL_CALC_FOUND_ROWS function is a nice way to return how many rows were returned in the query. There has been a lot of discussion in the PHP.net entry on mysql_num_rows regarding this function. The debate centers around whether its more effecient to use MySQLs built in functionality or whether its more effecient to run the same query again using the COUNT() function.
For me, its hard to determine which way is better. Usually its better to leverage your database engine than code. There is not an easy way to tell how database cache plays into this either. I feel using SQL_CALC_FOUND_ROWS is the better option, it eliminates a few extra lines of code, and prevents you from having to update multiple queries. Whether there is a performance penalty in either case is debatable, if its even noticeable…
1 | SELECT SQL_CALC_FOUND_ROWS * FROM tbl_customer WHERE entry_date > '2009-01-01'; |
In a separate query run this (I believe this is connection dependent, so they must be run in conjunction with each other within the life of the same connection).
1 | SELECT FOUND_ROWS() AS totalRows; |
Tags: found_rows, mysql, sql_calc_found_rows