I have a query,
e.g.
name column have "Rodrigue Dattatray Desilva".
I want to write a query in such a way that,
If I search for 'gtl' and match anywhere in string it should show the result.
I know in PHP I can apply the patch like '%g%t%l%'.
But I want to know MySql way.
Note: I can search for anything, I am just giving above an example.
EDIT:
create table Test(id integer, title varchar(100));
insert into Test(id, title) values(1, "Rodrigue Dattatray Desilva");
select * from Test where title like '%g%t%l%';
Consider the above case. Where "gtl" is string I am trying to search in the title but search string can be anything.
gtl is string where it exists in the current title but not in sequence.
The easy answer is that you need an extra wildcard:
select * from Test where title like '%g%t%l%';
The query you posted does not have a wild card after the 'l', so would only match if the phrase ended with 'l'.
The more complicated answer is that you can also use regular expressions, which give you more power over the search.
The even more complicated answer is that performance of these string matching queries tends to be poor - the wild cards mean that indexes are usually ineffective. If you have a large number of rows in your table, full-text searching is much faster.
You can do the same in Mysql too.
You can use the keyword like in MySql.
% - The percent sign represents zero, one, or multiple characters
_ - The underscore represents a single character
Related
This may be a newbie question, as I'm not an expert in SQL. However, couldn't find the answer using Google.
I have a table called record_fields which contains the majority of my system's content, which I want to search in. The content cell is defined as LONGTEXT as it can include extremely long input.
Originally, I used (simplifying the query a bit for clarity sake):
SELECT * FROM record_fields WHERE LOWER(content) LIKE LOWER('%{$keyword}%')
Execution time aside, this query has one major issue. If I search for the term "post" it will return all content which has words like "poster", "posting" and others. I wanted to add a FULLTEXT search.
Now the query looks like this (again, simplified):
SELECT * FROM record_fields WHERE MATCH (content) AGAINST ('{$keyword}')
However, this is still problematic. With MATCH, if my system's users search for the words "Bank of America", for example, all records that either have the word "Bank" and "America" will be returned.
TL;DR - my question is this:
how do I use MATCH to search for exact phrases with space in them?
Any help would be highly appreciated, thanks in advance!
%{keyword}% matches all text sub-strings that include your keyword anywhere in the string. MATCH usually takes all keywords in the match string as individual search terms, and matches against each. You can use boolean mode and use a + symbol before each required keyword. Take a look at the MySQL reference for this.
Edited the answer to reflect Idan's response in not getting the results from the suggested %keyword solution.
You can use Match Against With Boolean Mode and you can put your input string inside '"{$keyword}"'.
Check last example in below link
https://dev.mysql.com/doc/refman/5.5/en/fulltext-boolean.html
SELECT * FROM record_fields WHERE MATCH (content) AGAINST ('"{$keyword}"' IN BOOLEAN MODE )
I want to query a table as follows:
I have a field called "category" and my input match contains N separate words. I want the query to match all rows that contain all N words, but in any order.
For example if the field category contains "hello good morning world", my input query can contain "hello morning" or "good" or "world hello" and all are matches to the query.
How do I formulate such an SQL expression?
Also it would be good if the query can be made case insensitive.
If you are using MySQL you can use the boolean fulltext search feature to achieve this. You can put a + in front of each term and then only results with all the terms, in any order, will be returned. You will need to make sure the column containing the category field has a fulltext index specified on it for this to work. Other database engines probably have similar features. So for example you might do something like the following assuming there were a fulltext index over the category column...
SELECT * FROM myTable WHERE MATCH (category) AGAINST ('+term1 +term2 +term3' IN BOOLEAN MODE);
I would avoid using the "LIKE" operator as others have suggested you would have to worry about the headache of mixed upper/lower case and if you have a large database using a % in the front of a LIKE search term is going to cause a full table scan instead of using an index which is horrible for performance.
I'm not writing the loop that will build this query for you. This will get the job done, but it will be pretty inefficient.
SELECT * FROM table
WHERE (
TOUPPER(category) LIKE '*HELLO*' AND
TOUPPER(category) LIKE '*GOOD*' AND
TOUPPER(category) LIKE '*MORNING*' AND
TOUPPER(category) LIKE '*WORLD*'
);
You could also research using REGEXes with SQL.
I have a PHP interface with a keyword search, working off a DB(MySQL) which has a Keywords field.
The way in which the keywords field is set up is as follows, it is a varchar with all the words formatted as shown below...
the, there, theyre, their, thermal etc...
if i want to just return the exact word 'the' from the search how would this be achieved?
I have tried using 'the%' and '%the' in the PHP and it fails to work by not returning all of the rows where the keyword appears in.
is there a better (more accurate) way to go about this?
Thanks
If you want to select the rows that have exactly the keyword the:
SELECT * FROM table WHERE keyword='the'
If you want to select the rows that have the keyword the anywhere in them:
SELECT * FROM table WHERE keyword LIKE '%the%'
If you want to select the rows that start with the keyword the:
SELECT * FROM table WHERE keyword LIKE 'the%'
If you want to select the rows that end with the keyword the:
SELECT * FROM table WHERE keyword LIKE '%the'
Try this
SELECT * FROM tablename
WHERE fieldname REGEXP '[[:<:]]test[[:>:]]'
[[:<:]] and [[:>:]] are markers for word boundaries.
MySQL Regular Expressions
if you also search for the commas, you can be sure you are getting the whole word.
where keywordField like '%, the, %'
or keywordField like '%, the'
or keywordField like 'the, %'
maybe I didn't understand the question properly... but If you want all the words where 'the' appears, a LIKE '%word%' should work.
If the DB of words is HUGE MySQL may fail to retrieve some of the words, that can be solved in 2 ways...
1- get a DB that support bigger sizes (not many ppl would chose this one tho). For example SQL Server has a 'CONTAINS' function that works better than LIKE '%word%'.
2- use a external search tool that uses inverted index search. I used Sphinx for a project and it works quite good. This is better if you rarely UPDATE the rows of the data you want to search from, which should be the case.
Sphinx for example would generate a file from your MySQL table and use this file to solve the search (it's very fast), this file should be re-indexed everytime you do a insert or update on the table, making it a much better solution if you rarely update or insert new rows.
It looks like you have a one to many relationship going on within a column. It might be better to create a separate table for keywords with a row for each keyword and a foreign key to whatever it is you're searching on.
Doing like '%???%' is generally a bad idea because the DB can't make use of an index so it will scan the whole table. Whether this matters will depend on the size of data you're working with but its worth considering up front. The single best way to help DB performance is in the initial table design. This can be tricky to change later.
I am building a search feature for the messages part of my site, and have a messages database with a little over 9,000,000 rows, and and index on the sender, subject, and message fields. I was hoping to use the LIKE mysql clause in my query, such as (ex)
SELECT sender, subject, message FROM Messages WHERE message LIKE '%EXAMPLE_QUERY%';
to retrieve results. unfortunately, MySQL doesn't use indexes when a leading wildcard is present , and this is necessary for the search query could appear anywhere in the message (this is how the wildcards work, no?). Queries are very very slow and I cannot use a full text index either, because of the annoying 50% rule (I just can't afford to rule that much out). Is there anyway (or even, any alternative to this) to optimize a query using like and two wildcards? Any help is appreciated.
You should either use full-text indexes (you said you can't), design a full-text search by yourself or offload the search from MySQL and use Sphinx/Lucene. For Lucene you can use Zend_Search_Lucene implementation from Zend Framework or use Solr.
Normal indexes in MySQL are B+Trees, and they can't be used if the starting of the string is not known (and this is the case when you have wildcard in the beginning)
Another option is to implement search on your own, using reference table. Split text in words and create table that contains word, record_id. Then in the search you split the query in words and search for each of the words in the reference table. In this way you are not limitting yourself to the beginning of the whole text, but only to the beginning of the given word (and you'll match the rest of the words anyway)
'%EXAMPLE_QUERY%'; is a very very bad idea .. am going to give you some
A. Avoid wildcards at the start of LIKE queries use 'EXAMPLE_QUERY%'; instead
B. Create Keywords where you can easily use MATCH
If you want to stick with using MySQL, you should use FULL TEXT indexes. Full text indexes index words in a text block. You can then search on word stems and return the results in order of relevance. So you can find the word "example" within a block of text, but you still can't search efficiently on "xampl" to find "example".
MySQL's full text search is not great, but it is functional.
http://dev.mysql.com/doc/refman/5.1/en/fulltext-search.html
select * from emp where ename like '%e';
gives emp_name that ends with letter e.
select * from emp where ename like 'A%';
gives emp_name that begins with letter a.
select * from emp where ename like '_a%';
gives emp_name in which second letter is a.
This question is a chalenge for me, my friend can`t tell me how to do it, but he is really good programmer (I think).
Users can put into database sentences. When user puts a sentence it is saved in sentences table.
Next, sentence is split into words, each soundex of the word is saved into table tags with id of the splited sentence.
Last, each soundax of the word is put into weights table, if there arleady is the same soundex, function adds 1 to counter of this soundex.
(For those who dont know: soundex is a function that returns a phonetic representation (the way it sounds) of a string)
Structure of the database:
One table sentences contains two rows: id and sentence.
Other table tags contains id (with is id of a sentence) and tag (with is one word from the sentence).
tag isn't really just plain word, but soundex of this word.
Last table weights contains tag and weight (with is number, it tells us how many there is tags like this in table tags)
My question is: how can I make a function witch returns similar sentences to given string.
It should use tags (soundex of word) and each tag should have its own power based on weights table.
Tags, that are often used are more important, then more original tags. Can it be done in just one mysql query?
Next question: I think that this way of looking for similar sentences is good, but what with speed of this function?
I need to use it very very often in my site.
Well instead of having a weights table, why don't you have a table that relates tags to sentences? So have a table called sentence_tags with a sentence_id and a tag_id column. Then you can compute the weights by doing a join on those two tables, and still reference back to the sentence that contains the tag. You may as well store both the tag and the soundex in the tags table, while you're at it.
Perhaps the Levenshtein Distance is what you are looking for. It calculates the number of steps there are needed to transfer from one word to another.
Do realize this is a costly operation.
Joe K's suggestion seems spot on for good database design.
Do not store information that can be extrapolated.
Meaning, use the join statement and PHP to calculate the weight at run-time.
I understand this may not be the correct solution in your design, but often a few moments spent on smart database struture design will make everything work that much better.