SQL：将IN运算符与任何内容匹配

Question

I am trying to build a dynamic query.

This works fine :

$qstring="10000, 10001, 10003, 10005";

SELECT *
FROM orders
WHERE order_id in ($qstring);

This also works fine when I have no data to match and select.

$qstring="";

SELECT *
FROM orders
WHERE order_id in ($qstring);

Does something like below exists to match any data? I checked out the pattern matching for SQL but found nothing that could match everything.

$qstring="*";

SELECT *
FROM orders
WHERE order_id in ($qstring);

Any hints? Thanks!

Answer 1

So, you need to make your query:

SELECT *
FROM orders
WHERE order_id in ($qstring);

Works fine in case there was no values passed in the @qstring parameter. In this case try this instead:

SELECT * FROM orders 
WHERE ($qstring <> '*' AND order_id in ($qstring));

Answer 2

If you want to match everything just use the select without the where clause.

SELECT * FROM orders

If you're forced (for some odd reason to use the construct you described) then...

$qstring="SELECT order_id FROM orders";

Answer 3

In case you need everything you should not have a WHERE IN clause.

Check your $qstring variable and only append the WHERE order_id in ($qstring); when neccessary