I have the following SQL query:
SELECT Phrases.*
FROM Phrases
WHERE (((Phrases.phrase) Like "*ing aids*")
AND ((Phrases.phrase) Not Like "*getting*")
AND ((Phrases.phrase) Not Like "*contracting*"))
AND ((Phrases.phrase) Not Like "*preventing*"); //(etc.)
Now, if I were using RegEx, I might bunch all the Nots into one big (getting|contracting|preventing), but I'm not sure how to do this in SQL.
Is there a way to render this query more legibly/elegantly?
Just by removing redundant stuff and using a consistent naming convention your SQL looks way cooler:
SELECT *
FROM phrases
WHERE phrase LIKE '%ing aids%'
AND phrase NOT LIKE '%getting%'
AND phrase NOT LIKE '%contracting%'
AND phrase NOT LIKE '%preventing%'
You talk about regular expressions. Some DBMS do have it: MySQL, Oracle... However, the choice of either syntax should take into account the execution plan of the query: "how quick it is" rather than "how nice it looks".
With MySQL, you're able to use regular expression where-clause parameters:
SELECT something FROM table WHERE column REGEXP 'regexp'
So if that's what you're using, you could write a regular expression string that is possibly a bit more compact that your 4 like criteria. It may not be as easy to see what the query is doing for other people, however.
It looks like SQL Server offers a similar feature.
Sinec it sounds like you're building this as you go to mine your data, here's something that you could consider:
CREATE TABLE Includes (phrase VARCHAR(50) NOT NULL)
CREATE TABLE Excludes (phrase VARCHAR(50) NOT NULL)
INSERT INTO Includes VALUES ('%ing aids%')
INSERT INTO Excludes VALUES ('%getting%')
INSERT INTO Excludes VALUES ('%contracting%')
INSERT INTO Excludes VALUES ('%preventing%')
SELECT
*
FROM
Phrases P
WHERE
EXISTS (SELECT * FROM Includes I WHERE P.phrase LIKE I.phrase) AND
NOT EXISTS (SELECT * FROM Excludes E WHERE P.phrase LIKE E.phrase)
You are then always just running the same query and you can simply change what's in the Includes and Excludes tables to refine your searches.
Depending on what SQL server you are using, it may support REGEX itself. For example, google searches show that SQL Server, Oracle, and mysql all support regex.
You could push all your negative criteria into a short circuiting CASE expression (works Sql Server, not sure about MSAccess).
SELECT *
FROM phrases
WHERE phrase LIKE '%ing aids%'
AND CASE
WHEN phrase LIKE '%getting%' THEN 2
WHEN phrase LIKE '%contracting%' THEN 2
WHEN phrase LIKE '%preventing%' THEN 2
ELSE 1
END = 1
On the "more efficient" side, you need to find some criteria that allows you to avoid reading the entire Phrases column. Double sided wildcard criteria is bad. Right sided wildcard criteria is good.
Related
I have a large list of SQL commands such as
SELECT * FROM TEST_TABLE
INSERT .....
UPDATE .....
SELECT * FROM ....
etc. My goal is to parse this list into a set of results so that I can easily determine a good count of how many of these statements are SELECT statements, how many are UPDATES, etc.
so I would be looking at a result set such as
SELECT 2
INSERT 1
UPDATE 1
...
I figured I could do this with Regex, but I'm a bit lost other than simply looking at everything string and comparing against 'SELECT' as a prefix, but this can run into multiple issues. Is there any other way to format this using REGEX?
You can add the SQL statements to a table and run them through a SQL query. If the SQL text is in a column called SQL_TEXT, you can get the SQL command type using this:
upper(regexp_substr(trim(regexp_replace(SQL_TEXT, '\\s', ' ')),
'^([\\w\\-]+)')) as COMMAND_TYPE
You'll need to do some clean up to create a column that indicates the type of statement you have. The rest is just basic aggregation
with cte as
(select *, trim(lower(split_part(regexp_replace(col, '\\s', ' '),' ',1))) as statement
from t)
select statement, count(*) as freq
from cte
group by statement;
SQL is a language and needs a parser to turn it from text into a structure. Regular expressions can only do part of the work (such as lexing).
Regular Expression Vs. String Parsing
You will have to limit your ambition if you want to restrict yourself to using regular expressions.
Still you can get some distance if you so want. A quick search found this random example of tokenizing MySQL SQL statements using regex https://swanhart.livejournal.com/130191.html
I need to find the '&' in a string.
SELECT * FROM TABLE WHERE FIELD LIKE ..&...
Things we have tried :
SELECT * FROM TABLE WHERE FIELD LIKE '&&&'
SELECT * FROM TABLE WHERE FIELD LIKE '&\&&'
SELECT * FROM TABLE WHERE FIELD LIKE '&|&&' escape '|'
SELECT * FROM TABLE WHERE FIELD LIKE '&[&]&'
None of these give any results in SQLServer.
Well some give all rows, some give none.
Similar questions that didn't work or were not specific enough.
Find the % character in a LIKE query
How to detect if a string contains special characters?
some old reference Server 2000
http://web.archive.org/web/20150519072547/http://sqlserver2000.databases.aspfaq.com:80/how-do-i-search-for-special-characters-e-g-in-sql-server.html
& isn't a wildcard in SQL, therefore no escaping is needed.
Use % around the value your looking for.
SELECT * FROM TABLE WHERE FIELD LIKE '%&%'
Your statement contains no wildcards, thus is equivalent to WHERE FIELD = '&'.
& isn't a special character in SQL so it doesn't need to be escaped. Just write
WHERE FIELD LIKE '%&%'
to search for entries that contain & somewhere in the field
Be aware though, that this will result in a full table scan as the server can't use any indexes. Had you typed WHERE FIELD LIKE '&%' the server could do a range seek to find all entries starting with &.
If you have a lot of data and can't add any more constraints, you should consider using SQL Server's full-text search to create and use and FTS index, with predicates like CONTAINS or FREETEXT
I'm currently trying to integrate Sphinx search engine into Python application. The problem is that SphinxQL doesn't support OR clause as common SQL does. There are some hacks to use, like writing expressions in SELECT like this:
SELECT id,(field1 = val1 OR field2 = val2) as expr FROM foo_bar WHERE expr = 1;
However, it doesn't work with strings, because they should be handled using MATCH function. So I decided to divide query into separate subqueries and combine results obtained. Yet there's still a problem of getting a proper META information, especially the total_found field. Sphinx counts it for separate queries, but rows obtained from these queries may intersect and I have no ability to check it (database is large).
I believe there must be a solution. I'm using Sphinxit (SphinxAlchemy has a version conflict with SQLAlchemy I'm using).
Repost from SphinxSearch forum:
I have a table I need to search in with text and numerical columns as well. I need to
write a query with OR condition; found out that there's a way to do it using SELECT
expressions like:
SELECT *, quantity>=50 OR quantity=0 AS mycond FROM table1 WHERE mycond = 1;
Hopelessly it doesn't work with string attributes. This query isn't parsed:
SELECT *, category='foo' OR category='bar' AS mycond FROM table1 WHERE mycond = 1;
Yet this is working in Beta 2.2.3:
SELECT * FROM table1 WHERE category='foo';
What should I do to find count of rows that fit one of conditions, not every one of them?
I can make a few queries and merge obtained items into one list, but I need to now how
much of these rows are in the database now.
For attribute / facet OR'ing, I think you're correct that the only way is to put an expression in the SELECT clause.
For strings, though, check out the documentation on the fulltext query syntax. You can't exactly use the OR keyword, but something like this should work:
SELECT id, name
FROM recipes
WHERE MATCH('(#ingredients chocolate) | (#name cake)')
LIMIT 10;
This question already has answers here:
Is there a combination of "LIKE" and "IN" in SQL?
(28 answers)
Closed 9 years ago.
I would like to do something like this i.e., use wild card characters in the in clause:
SELECT * FROM mytable WHERE keywords IN ('%test%', '%testing%')
This is not supported in SQL Server.... Is there some other way to achieve it...
Looking for something other than:
SELECT * FROM mytable WHERE keywords like '%test%' or keywords like '%testing%' or.....
Nope, only other way I can think of is joining in to a temp table but then you have to eliminate duplicate rows.
This query of yours is horribly inefficient as it will unconditionally table scan. Perhaps you should look at separating the keywords or introducing a full text index.
If you would like to look into doing full text searches, then I would recommend looking into some of the heavy weights out there like sphinx or lucene when you evaluate the Sql Server full-text solution.
SELECT DISTINCT *
FROM
mytable M
JOIN
(
SELECT '%test%' AS pattern
UNION ALL SELECT '%testing%'
...
) foo ON M.keywords LIKE foo.Pattern
Could be a CTE or temp table too
This is not supported in MS SQL.... Is
there some other way to achieve it?
Yes, Full Text Search. At least for prefix wildcards.
You can use Regular Expression to do this.
In one Regular Expression you can define as many pattern as you want in one expression.
There are lot's of article about Regular Expression Matching in MS SQL SERVER.
I used RLIKE in MySQL to do Regular Expression Matching.
I also attached link1 & link2 for MS SQL SERVER Regular Expression Matching.
I am new to SQL programming.
I have a table job where the fields are id, position, category, location, salary range, description, refno.
I want to implement a keyword search from the front end. The keyword can reside in any of the fields of the above table.
This is the query I have tried but it consist of so many duplicate rows:
SELECT
a.*,
b.catname
FROM
job a,
category b
WHERE
a.catid = b.catid AND
a.jobsalrange = '15001-20000' AND
a.jobloc = 'Berkshire' AND
a.jobpos LIKE '%sales%' OR
a.jobloc LIKE '%sales%' OR
a.jobsal LIKE '%sales%' OR
a.jobref LIKE '%sales%' OR
a.jobemail LIKE '%sales%' OR
a.jobsalrange LIKE '%sales%' OR
b.catname LIKE '%sales%'
For a single keyword on VARCHAR fields you can use LIKE:
SELECT id, category, location
FROM table
WHERE
(
category LIKE '%keyword%'
OR location LIKE '%keyword%'
)
For a description you're usually better adding a full text index and doing a Full-Text Search (MyISAM only):
SELECT id, description
FROM table
WHERE MATCH (description) AGAINST('keyword1 keyword2')
SELECT
*
FROM
yourtable
WHERE
id LIKE '%keyword%'
OR position LIKE '%keyword%'
OR category LIKE '%keyword%'
OR location LIKE '%keyword%'
OR description LIKE '%keyword%'
OR refno LIKE '%keyword%';
Ideally, have a keyword table containing the fields:
Keyword
Id
Count (possibly)
with an index on Keyword. Create an insert/update/delete trigger on the other table so that, when a row is changed, every keyword is extracted and put into (or replaced in) this table.
You'll also need a table of words to not count as keywords (if, and, so, but, ...).
In this way, you'll get the best speed for queries wanting to look for the keywords and you can implement (relatively easily) more complex queries such as "contains Java and RCA1802".
"LIKE" queries will work but they won't scale as well.
Personally, I wouldn't use the LIKE string comparison on the ID field or any other numeric field. It doesn't make sense for a search for ID# "216" to return 16216, 21651, 3216087, 5321668..., and so on and so forth; likewise with salary.
Also, if you want to use prepared statements to prevent SQL injections, you would use a query string like:
SELECT * FROM job WHERE `position` LIKE CONCAT('%', ? ,'%') OR ...
I will explain the method i usally prefer:
First of all you need to take into consideration that for this method you will sacrifice memory with the aim of gaining computation speed.
Second you need to have a the right to edit the table structure.
1) Add a field (i usually call it "digest") where you store all the data from the table.
The field will look like:
"n-n1-n2-n3-n4-n5-n6-n7-n8-n9" etc.. where n is a single word
I achieve this using a regular expression thar replaces " " with "-".
This field is the result of all the table data "digested" in one sigle string.
2) Use the LIKE statement %keyword% on the digest field:
SELECT * FROM table WHERE digest LIKE %keyword%
you can even build a qUery with a little loop so you can search for multiple keywords at the same time looking like:
SELECT * FROM table WHERE
digest LIKE %keyword1% AND
digest LIKE %keyword2% AND
digest LIKE %keyword3% ...
You can find another simpler option in a thread here: Match Against.. with a more detail help in 11.9.2. Boolean Full-Text Searches
This is just in case someone need a more compact option. This will require to create an Index FULLTEXT in the table, which can be accomplish easily.
Information on how to create Indexes (MySQL): MySQL FULLTEXT Indexing and Searching
In the FULLTEXT Index you can have more than one column listed, the result would be an SQL Statement with an index named search:
SELECT *,MATCH (`column`) AGAINST('+keyword1* +keyword2* +keyword3*') as relevance FROM `documents`USE INDEX(search) WHERE MATCH (`column`) AGAINST('+keyword1* +keyword2* +keyword3*' IN BOOLEAN MODE) ORDER BY relevance;
I tried with multiple columns, with no luck. Even though multiple columns are allowed in indexes, you still need an index for each column to use with Match/Against Statement.
Depending in your criterias you can use either options.
I know this is a bit late but what I did to our application is this. Hope this will help someone tho. But it works for me:
SELECT * FROM `landmarks` WHERE `landmark_name` OR `landmark_description` OR `landmark_address` LIKE '%keyword'
OR `landmark_name` OR `landmark_description` OR `landmark_address` LIKE 'keyword%'
OR `landmark_name` OR `landmark_description` OR `landmark_address` LIKE '%keyword%'