multiple search criteria

Question

I'm using the following query, but I currently have to enter a value in every parameter for the query to work. Is there a way of making the parameters optional, so that 1 or more values will return a result?

SELECT * FROM film
WHERE day LIKE '%day%'
AND month LIKE '%month%'
AND year LIKE '%year%'

---

something like

 function queryData(year,month,day) 

 declare Y

 if year == nothing
     Y = '%'
 else
     Y = '%' + year + '%'

 declare M

 if month == nothing
     M = '%'
 else
     M = '%' + month + '%'

 declare D

 if day == nothing
     D = '%'
 else
     D = '%' + day + '%'

 return result of :

 SELECT * FROM film
 WHERE day LIKE D
 OR month LIKE M
 OR year LIKE Y

Answer 1

Why don't you create your query dynamically? Depending on the parameters you have, append the filters dynamically.

eg:

string query = "SELECT * FROM film";
string paramenters = string.empty;

if(day!= string.empty)
  parameters = " Where day LIKE '%day%'";

if(month != string.empty)
{
  if(parameters != string.empty)
     parameters += "AND month LIKE '%month%'";
  else
     parameters = "WHERE month LIKE '%month%'";
}

and so on....

In this case you won't get extra results that you will get with OR .

Answer 2

SELECT * FROM film
WHERE day LIKE '%day%'
OR month LIKE '%month%'
OR year LIKE '%year%'

You will still be providing all three parameters, but it won't matter if they are blank or NULL, matches will still return from the ones that aren't blank.

Answer 3

Using OR instead of AND changes the logic of the query. It doesn't make the parameters optional. The way to go is not using the parameters you are not using. I don't know any other way.

Answer 4

我会将每个参数的默认值设为％，当有人填写参数时，我会传递％value％

Answer 5

I've not tested, but your query looks like it should work as long as you make sure that the unused parameters are empty strings. eg

day = ""
month = "dec"
year = "2008"

would make your query:

SELECT * FROM film
WHERE day LIKE '%%'
AND month LIKE '%dec%'
AND year LIKE '%2008%'

'%%' should match any string as long as it's not NULL.

Answer 6

thanks for your help folks I ended implementing the following. works a treat

if year == nothing
   Y = ''
else
   Y = '%' + year + '%'

Answer 7

If you wish for a non-dynamic query, something like this will work:

SELECT * FROM film
WHERE (:daysearch is null or day LIKE :daysearch)
AND (:monthsearch is null or month LIKE :monthsearch)
AND (:yearsearch is null or year LIKE :yearsearch)

Although, I do wonder if there is a performance hit on the database.