i want select similar rows accourding to row's title columun. Title columun has mostly have 5 or 6 six keywords. Which algorithm do you recommend ? Soundex Maybe ?
P.S: Title columun has unicode chracters like Ç, Ö, Ş...
My question's answer mysql full text search. Also it supports unicode.
SELECT *, match(project_title) against('sample project 55') as similarity
FROM projects
WHERE status IN(1, 2, 3, 4, 5, 6) AND id != ? AND match('sample project 55') against(?)
ORDER BY similarity DESC
If you mean similar in spelling and pronunciation, I'd look into using the SOUNDEX function.
Honestly, I'd create a table for keywords(id, external_id, keyword), and then I would join the table against itself, order by how many matches there are, and then grab the rows back out.
If you're matching against a single row, you can select only that one, for much better efficiency with the join.
This could be combined with SOUNDEX to match together things that are close
Related
I have a column storing codes like 71xxxx, 78xxxx, 59xxxx, and so on. I need to run a query to find out all the records that have codes starting with 71.
I mean, all the rows where the the first two digits of the code column are 71. If anyone can share the SQL query for this, I would be really helpful.
Thanks.
You would use like in a where clause for the filtering:
where code like '71%'
This is pretty basic SQL. If you are not familiar with it, you should study the language a bit more.
Try this
select substr(col, 1,2),count(*) from ITEM group by substr(col, 1,2)
I guess this has been asked in the site before but I can't find it.
I've seen in some sites that there is a vague count over the results of a search. For example, here in stackoverflow, when you search a question, it says +5000 results (sometimes), in gmail, when you search by keywords, it says "hundreds" and in google it says aprox X results. Is this just a way to show the user an easy-to-understand-a-huge-number? or this is actually a fast way to count results that can be used in a database [I'm learning Oracle at the moment 10g version]? something like "hey, if you get more than 1k results, just stop and tell me there are more than 1k".
Thanks
PS. I'm new to databases.
Usually this is just a nice way to display a number.
I don't believe there is a way to do what you are asking for in SQL - count does not have an option for counting up until some number.
I also would not assume this is coming from SQL in either gmail, or stackoverflow.
Most search engines will return a total number of matches to a search, and then let you page through results.
As for making an exact number more human readable, here is an example from Rails:
http://api.rubyonrails.org/classes/ActionView/Helpers/NumberHelper.html#method-i-number_to_human
With Oracle, you can always resort to analytical functions in order to calculate the exact number of rows about to be returned. This is an example of such a query:
SELECT inner.*, MAX(ROWNUM) OVER(PARTITION BY 1) as TOTAL_ROWS
FROM (
[... your own, sorted search query ...]
) inner
This will give you the total number of rows for your specific subquery. When you want to apply paging as well, you can further wrap these SQL parts as such:
SELECT outer.* FROM (
SELECT * FROM (
SELECT inner.*,ROWNUM as RNUM, MAX(ROWNUM) OVER(PARTITION BY 1) as TOTAL_ROWS
FROM (
[... your own, sorted search query ...]
) inner
)
WHERE ROWNUM < :max_row
) outer
WHERE outer.RNUM > :min_row
Replace min_row and max_row by meaningful values. But beware that calculating the exact number of rows can be expensive when you're not filtering using UNIQUE SCAN or relatively narrow RANGE SCAN operations on indexes. Read more about this here: Speed of paged queries in Oracle
As others have said, you can always have an absolute upper limit, such as 5000 to your query using a ROWNUM <= 5000 filter and then just indicate that there are more than 5000+ results. Note that Oracle can be very good at optimising queries when you apply ROWNUM filtering. Find some info on that subject here:
http://www.dba-oracle.com/t_sql_tuning_rownum_equals_one.htm
Vague count is a buffer which will be displayed promptly. If user wants to see more results then he can request more.
It's a performance facility, after displaying the results the sites like google keep searching for more results.
I don't know how fast this will run, but you can try:
SELECT NULL FROM your_tables WHERE your_condition AND ROWNUM <= 1001
If count of rows in result will equals to 1001 then total count of records will > 1000.
this question gives some pretty good information
When you do an SQL query you can set a
LIMIT 0, 100
for example and you will only get the first hundred answers. so you can then print to your viewer that there are 100+ answers to their request.
For google I couldn't say if they really know there is more than 27'000'000'000 answer to a request but I believe they really do know. There are some standard request that have results stored and where the update is done in the background.
Use:
The user searches for a partial postcode such as 'RG20' which should then be displayed in a specific order. The query uses the MATCH AGAINST method in boolean mode where an example of the postcode in the database would be 'RG20 7TT' so it is able to find it.
At the same time it also matches against a list of other postcodes which are in it's radius (which is a separate query).
I can't seem to find a way to order by a partial match, e.g.:
ORDER BY FIELD(postcode, 'RG20', 'RG14', 'RG18','RG17','RG28','OX12','OX11')
DESC, city DESC
Because it's not specifically looking for RG20 7TT, I don't think it can make a partial match.
I have tried SUBSTR (postcode, -4) and looked into left and right, but I haven't had any success using 'by field' and could not find another route...
Sorry this is a bit long winded, but I'm in a bit of a bind.
A UK postcode splits into 2 parts, the last section always being 3 characters and within my database there is a space between the two if that helps at all.
Although there is a DESC after the postcodes, I do need them to display in THAT particular order (RG20, RG14 then RG18 etc..) I'm unsure if specifying descending will remove the ordering or not
Order By Case
When postcode Like 'RG20%' Then 1
When postcode Like 'RG14%' Then 2
When postcode Like 'RG18%' Then 3
When postcode Like 'RG17%' Then 4
When postcode Like 'RG28%' Then 5
When postcode Like 'OX12%' Then 6
When postcode Like 'OX11%' Then 7
Else 99
End Asc
, City Desc
You're on the right track, trimming the field down to its first four characters:
ORDER BY FIELD(LEFT(postcode, 4), 'RG20', 'RG14', ...),
-- or SUBSTRING(postcode FROM 1 FOR 4)
-- or SUBSTR(postcode, 1, 4)
Here you don't want DESC.
(If your result set contains postcodes whose prefixes do not appear in your FIELD() ordering list, you'll have a bit more work to do, since those records will otherwise appear before any explicitly ordered records you specify. Before 'RG20' in the example above.)
If you want a completely custom sorting scheme, then I only see one way to do it...
Create a table to hold the values upon which to sort, and include a "sequence" or "sort_order" field. You can then join to this table and sort by the sequence field.
One note on the sequence field. It makes sense to create it as an int as... well, sequences are often ints :)
If there is any possibility of changing the sort order, you may want to consider making it alpha numeric... It is a lot easier to insert "5A" between "5 and "6" than it is to insert a number into a sequence of integers.
Another method I use is utilising the charindex function:
order by charindex(substr(postcode,4,1),"RG20RG14RG18...",1)
I think that's the syntax anyway, I'm just doing this in SAS at the moment so I've had to adapt from memory!
But essentially the sooner you hit your desired part of the string, the higher the rank.
If you're trying to rank on a large variety of postcodes then a case statement gets pretty hefty.
Hello: I want to do a "weighted search" on product that are tagged with keywords.
(So: not fulltext search, but n-to-m-relation). So here it is:
Table 'product':
sku - the primary key
name
Table 'keywords':
kid - keyword idea
keyword_de - German language String (e.g. 'Hund','Katze','Maus')
keyword_en - English language String (e.g. 'Dog','Cat','Mouse')
Table 'product_keyword' (the cross-table)
sku \__ combined primary key
kid /
What I want is to get a score for all products that at least "contain" one relevant keyword. If I search for ('Dog','Elephant','Maus') I want that
Dog credits a score of 1.003,
Elephant of 1.002
Maus of 1.001
So least important search term starts at 1.001, everything else 0.001++. That way, a lower score limit of 3.0 would equal "AND" query (all three keywords must be found), a lower score limit of 1.0 would equal an "OR". Anything in between something more or less matching. In particular by sorting according to this score, most relevant search results would be first (regardless of lower limit)...
I guess I will have to do something with
IF( keyword1 == 'dog', 1.001, 0) + IF...
maybe inside a SUM() and probably with a GROUP BY at the end of a JOIN over the cross table, eh? But I am fairly clueless how to tackle this.
What would be feasible, is to get the keyword id's from the keywords beforehand. That's a cheap query. So the keywords table can be left ignored and it's all about the other of the cross and product table...
I have PHP at hand to automatically prepare a fairly lengthy PHP statement, but I would like to avoid further multiple SQL statements. In particular since I will limit the query outcome (most often to "LIMIT 0, 20") for paging mode results, so looping a very large number of in between results through a script would be no good...
DANKESCHÖN, if you can help me on this :-)
I think a lot of this is in the Lucene engine (http://lucene.apache.org/java/docs/index.html), which is available for PHP in the Zend Framework: http://framework.zend.com/manual/en/zend.search.lucene.html.
EDIT:
If you want to do the weighted thing you are talking about, I guess you could use something like this:
select p.sku, sum(case k.keyword_en when 'Dog' then 1001 when 'Cat' then 1002 when 'Mouse' then 1003 else 0 end) as totalscore
from products p
left join product_keyword pk on p.sku = pk.sku
inner join keywords k on k.kid = pk.kid
where k.keyword_en in ('Dog', 'Cat', 'Mouse')
group by p.sku
(Edit 2: forgot the group by clause.)
SELECT bp.*,r.rating,COUNT(r.review_for),bp.business_name,bp.profile_member
FROM ibf_business_reviews r
LEFT JOIN ibf_business_profiles bp ON ( r.review_for=bp.profile_member )
WHERE bp.sub_category LIKE '%{$id},%'{$location_sql}
GROUP BY r.review_for HAVING COUNT(r.review_for) >=1
ORDER BY r.date_posted DESC LIMIT 0,2");
This query is used to show results for business_name in a certain sub_category id '%{$id} in a certain location. My problem is that extra results are showing in categories that share a second or third digit aka ...viewcat&id=54 will show in ..viewcat&id=154 etc
I using the LIKE may be my issue? WHERE bp.sub_category LIKE '%{$id},%'
You are storing a comma-separated list in a varchar, when you should store one number per row in a child table. Then you wouldn't have to use LIKE at all.
Read up on First Normal Form.
Here was my comment
+! for the need to reformat the SQL. You do realize that the "percent"
signs (%) are the wildcards. So you're
essentially telling it that you can
return ANYTHING that includes id... so
if you search "23" you could get
"123", you could get "234" or
"1234"... etc.
and you replied
Thanks #Rock removing the wildcards worked!
Now my answer to this is... If you removed BOTH wildcards from your string, then you're essentially doing an "equals".
IE:
WHERE bp.sub_category LIKE '{$id},'
should be the same as
WHERE bp.sub_category = '{$id},'
Because you don't have any wildcards to "match" in the "LIKE" statement.
Please forgive me if I screwed up the "$" or the ","... I'm not a MySQL guy