如何订购和选择条件查询

Question

I have the following query:

SELECT * FROM table WHERE some conditions ORDER price ASC

The whole query is a bit more:

SELECT * FROM products WHERE some conditions ";
if (($_GET['Category']) =='X'){
switch( $_GET['price'] ){
    case '':
        $query_RS_Search .= ' some conditions ORDER BY price  ASC';
        break;
    case '0-500':
        $query_RS_Search .= ' some conditions ORDER BY price ASC';
        break;
    case '500-1000':
        etc
        break;  

}else{switch( $_GET['price'] ){
case '':
        $query_RS_Search .= ' some conditions ORDER BY price  ASC';
        break;
    case '0-500':
        $query_RS_Search .= ' some conditions ORDER BY price ASC';
        break;
    case '500-1000':
        etc
        break;  }}

what I would like to do is the same query but is the price is 0.00 this need to be the last instead of the first.

For example I have the following products:

product 1 price £15
product 2 price £25
product 3 price £12
product 4 price £0

I would like to order them as follows:

product 3 £12
product 1 £15
product 2 £25
product 4 £0

However the order I get is:

product 4 £0
product 3 £12
product 1 £15
product 2 £25

Any help welcome

Answer 1

Instead of:

ORDER BY price ASC

use:

ORDER BY IF(price = 0, 1, 0), price ASC

Demo here

Answer 2

Assuming you want to order by price ascending except when price is 0 then it needs to be last.

ORDER BY (CASE WHEN price = 0 THEN 1 ELSE 0 END) ASC, price ASC

If your price contains the actual pound sign, first of all that isn't good database design, but second of all, you'll have to modify the query to:

ORDER BY (CASE WHEN price = '£0'  THEN 1 ELSE 0 END) ASC, price ASC

This way the first priority ordering happens by a pseudo field that is only 1 when the price is 0 and will be ordered ascending, this means any price != 0 will be first before and price == 0. After that, we continue to order by price ascending. in your example, this would be:

product 3 £12
product 1 £15
product 2 £25
product 4 £0

Keep in mind, this will not work for any negative prices. If negative prices to also show up last, you'll have to modify the CASE statement to apply to price <= 0 instead.

Answer 3

Try: ORDER BY Price = 0, Price ASC

The Price = 0 condition in the ORDER BY clause will return a value of 0 or 1 if the result is false or true respectively. And by default it will be sorted in ascending order.

Therefore, the prices which are equal to 0 will have a result of 1 (true) base from the Price = 0 condition, and will be placed on the last rows because 1 (true) is greater than 0 (false) .

See the SQL Fiddle sample

Even if the data type of Price is DECIMAL , equating it to 0 or 0.00 will sort on the order that you want.

Take a look at this another SQL Fiddle sample.