使用多个SELECT语句来缩小结果范围

Question

I have a database with some properties that have been sold. They each have a date associated with it which is what I need to use to narrow the search results.

Basically I have a query:

$query = "SELECT * from newsales WHERE city = '".$_GET['location']."'";

And what I need to do is, from the results returned from the above query, I need to further narrow it down to be within the past 90 days.

So it'll find the city, and then it needs to ONLY get the ones from the last 90 days. How do I combine SELECT statements to narrow the results down?

Thanks!

Answer 1

You could use the SQL AND operator.

Doc: http://dev.mysql.com/doc/refman/5.1/en/logical-operators.html

Your query would be than:

$query = "SELECT * from newsales WHERE city = '".$_GET['location']."' AND date > '".$oldestdate."';

Set $date to the oldes date, in your case 90 days before today. According to your dateformat in your mysql database you have to calculate this in a timestamp or datetime.

Answer 2

You don't need to combine SELECT statements, just make a more complex WHERE clause using the boolean AND operator:

$query = "
    SELECT * 
    FROM newsales 
    WHERE 
        city = '".$_GET['location']."'
        AND date > '".$oldestdate."'
";

I'd advise you to read up on SQL injection as well - if you use $_GET directly like that, someone can come to your website and basically type in any SQL statement they want.

The easiest way, assuming you are using mysqli_* functions (which have replaced the mysql_* functions but can be used mostly interchangeably) is mysqli_real_escape_string() , eg city = '" . mysqli_real_escape_string($_GET['location']) . "' .

Answer 3

Combining results of multiple SELECT statements means you need to use UNION. Please see this : http://dev.mysql.com/doc/refman/5.0/en/union.html

(SELECT a FROM t1 WHERE a=10 AND B=1 ORDER BY a LIMIT 10)
UNION
(SELECT a FROM t2 WHERE a=11 AND B=2 ORDER BY a LIMIT 10);