Question

I am implementing a searching mechanism in a website and stumbled upon the SQL aspect of it.

The user can search for stories by any combination of these filters: story title, story tag, or the username of the story’s author. If no filter is provided, then just return all stories.

My immediate solution to this is this stored procedure:

(
@TitleFilter varchar(50) = NULL
,@TagFilter varchar(30) = NULL
,@UserFilter varchar(30) = NULL
)

SELECT
    story.Title
    ,story.AddedDTS

FROM
    Stories story
    INNER JOIN FREETEXTTABLE(Stories, Title, @TitleFilter) ft
        ON ft.[key] = story.ID
    LEFT JOIN StoryTags st
        ON st.StoryID = story.ID
    LEFT JOIN Tags tag
        ON tag.ID = st.TagID
    LEFT JOIN StoryUser su
        ON su.StoryID = story.ID
    LEFT JOIN Users u
        ON u.ID = su.UserID

WHERE
    1=1
    AND (
            (@TagFilter IS NULL AND @UserFilter IS NULL)
            OR (@TagFilter IS NOT NULL AND tag.Name = @TagFilter)
            OR (@UserFilter IS NOT NULL AND u.Username = @UserFilter)
        )

There’s a couple of problems with this, though, and I am yet to find a better approach.

First off, the Stories table has full-text search enabled, so I have to use the FREETEXTTABLE mechanism, which mandates the predicate to not be NULL, so this stored procedure will not work with @TitleFilter set to NULL.

Secondly, if I only search by title, then joining to StoryTags, Tags, StoryUsers, and Users tables are merely a useless overhead.

So the question is for both points I stated: can I conditionally omit joins to optimize the execution time?

If there’s a whole different approach to this, you are more than welcome to share it; I advocate thinking out of the box.

Answer 1

Given that when @TitleFilter is null it doesn’t work with FREETEXTTABLE I would either break it up with an if statement like so.

IF @TitleFilter is not null

    SELECT

        story.Title
        ,story.AddedDTS

    FROM
        Stories story
        INNER JOIN FREETEXTTABLE(Stories, Title, @TitleFilter) ft
         ON ft.[key] = story.ID
ELSE 

    SELECT
        story.Title
        ,story.AddedDTS

    FROM
        Stories story
        LEFT JOIN StoryTags st
        ON st.StoryID = story.ID
        LEFT JOIN Tags tag
        ON tag.ID = st.TagID
        LEFT JOIN StoryUser su
        ON su.StoryID = story.ID
        LEFT JOIN Users u
        ON u.ID = su.UserID
    WHERE

        (@TagFilter IS NULL AND @UserFilter IS NULL)
         OR (@TagFilter IS NOT NULL AND tag.Name = @TagFilter)
        OR (@UserFilter IS NOT NULL AND u.Username = @UserFilter)

Or if that offends you for some reason there’s always The Curse and Blessings of Dynamic SQL