I am using group by for like statement as i have database structure like this.
I want to get the count of workingzone groupby.but if i try to group by, then wrong output will appear as output will group by 99 and 99, as in figure.
My sql code is:
select count(organization),working_zone from `projects` where `district` = 12 and (`working_zone` = 99 or `working_zone` LIKE "99," or `working_zone` LIKE ",99") group by `organization`;
my desired result is:
count |working_zone
____6| 99
____3| 100
(99),(,99),(99,) should be grouped by doing sum and result should be 6.
You have an awful data structure -- although I wouldn't be surprised if the data is okay and you are really working off the result of a (reasonable) query. You should not be storing raw data in comma-delimited lists. Instead, use junction tables.
Why is having a separate row for each pair the SQLish way of storing data? Consider these reasons:
SQL has pretty based string functions (compared to other programming environments).
Data should be stored in its native type; don't store numbers as strings.
Foreign key relationships should be explicitly declared, and you can't declare a foreign key relationship using comma-delimited strings.
The primary SQL mechanism for optimizing queries are indexes, and comma-delimited lists preclude the use of indexes.
Sometimes, though, you are stuck with someone else's bad design decisions. If so, one solution uses a table of working zones:
select count(*), wz.working_zone
from projects p join
working_zones wz
on find_in_set(wz.working_zone, p.working_zone) > 0
where p.district; = 12 and
find_in_set(99, p.working_zone) > 0
group by wz.working_zone;
SELECT COUNT(organization),working_zone FROM table WHERE working_zone HAVING '99'
UNION ALL
SELECT COUNT(organization),SUBSTRING(working_zone,4) FROM table WHERE working_zone = '99,100'
Related
I am developing a php/mysql database. I have two tables - matters and actions.
Amongst other fields the matter table contains 'matterid' 'fixedfee' and 'fee'. Fixed fee is Y or N and the fee can be any number.
For any matter there can be a number of actions. The actions table contains 'actionid' 'matterid' 'advicetime' 'advicefee'. The advicetime is how long the advice goes on for (in decimal format) and advicefee is a number. Thus, to work out the cost of the advice for a matter I use SUM(advicetime*advicefee).
What I wish to do is to add up all of the 'fee' values when 'fixedfee'=Y and also the sum of all of the SUM(advicetime*advicefee) values for all of these matters.
I have tried using:
SELECT
SUM(matters.fee) AS totfixed,
SUM(advicetime*advicefee) AS totbills,
FROM matters
INNER JOIN actions
ON matters.matterid = actions.matterid
WHERE fixedfee = 'Y'
but this doesn't work as (I think) it is adding up the matters.fee for every time there is an action. I have also tried making it
SUM(DISTINCT matters.fee) AS totfixed
but this doesn't work as I think it seems to be missing out any identical fees (and there are several matters which have the same fixed fee).
I am fairly new to this so any help would be very welcome.
but this doesn't work as (I think) it is adding up the matters.fee for every time there is an action. I have also tried making it ...
You're experiencing aggregate fanout issue. This happens whenever the primary table in a select query has fewer rows than a secondary table to which it is joined. The join results in duplicate rows. So, when aggregate functions are applied, they act on extra rows.
Here the primary table refers to the one where aggregate functions are applied. In your example,
* SUM(matters.fee) >> aggregation on table matters.
* SUM(advicetime*advicefee) >> aggregation on table actions
* fixedfee='Y' >> where condition on table matters
To avoid the fanout issue:
* Always apply the aggregates to the most granular table in a join.
* Unless two tables have a one-to-one relationship, don't apply aggregate functions on fields from both tables.
* Obtain your aggregates separately through different subqueries and then combine the result. This can be done in a SQL statement, or you can export the data and then do it.
Query 1:
SELECT SUM(fee) AS totfixed
FROM matters
WHERE fixedfee='Y'
Query 2:
SELECT SUM(actions.advicetime*actions.advicefee) AS totbills
FROM matters
JOIN actions ON matters.matterid = actions.matterid
WHERE matters.fixedfee = 'Y'
Query 1 & Query 2 don't suffer from fanout. At this point you can export them both and deal with the result in php. Or you can combine them in SQL:
SELECT query_2.totbills, query_1.totfixed
FROM (SELECT SUM(fee) AS totfixed
FROM matters
WHERE fixedfee='Y') query_1,
(SELECT SUM(actions.advicetime*actions.advicefee) AS totbills
FROM matters
JOIN actions ON matters.matterid = actions.matterid
WHERE matters.fixedfee = 'Y') query_2
Finally, SUM does not take a keyword DISTINCT. DISTINCT is only available to COUNT and GROUP_CONCAT aggregate functions. The following is a piece of invalid SQL
SUM(DISTINCT matters.fee) AS totfixed
We have records with a count field on an unique id.
The columns are:
mainId = unique
mainIdCount = 1320 (this 'views' field gets a + 1 when the page is visited)
How can you insert all these mainIdCount's as seperate records in another table IN ANOTHER DBASE in one query?
Yes, I do mean 1320 times an insert with the same mainId! :-)
We actually have records that go over 10,000 times an id. It just has to be like this.
This is a weird one, but we do need the copies of all these (just) counts like this.
The most straightforward way to this is with a JOIN operation between your table, and another row source that provides a set of integers. We'd match each row from our original table to as many rows from the set of integer as needed to satisfy the desired result.
As a brief example of the pattern:
INSERT INTO newtable (mainId,n)
SELECT t.mainId
, r.n
FROM mytable t
JOIN ( SELECT 1 AS n
UNION ALL SELECT 2
UNION ALL SELECT 3
UNION ALL SELECT 4
UNION ALL SELECT 5
) r
WHERE r.n <= t.mainIdCount
If mytable contains row mainId=5 mainIdCount=4, we'd get back rows (5,1),(5,2),(5,3),(5,4)
Obviously, the rowsource r needs to be of sufficient size. The inline view I've demonstrated here would return a maximum of five rows. For larger sets, it would be beneficial to use a table rather than an inline view.
This leads to the followup question, "How do I generate a set of integers in MySQL",
e.g. Generating a range of numbers in MySQL
And getting that done is a bit tedious. We're looking forward to an eventual feature in MySQL that will make it much easier to return a bounded set of integer values; until then, having a pre-populated table is the most efficient approach.
I have a table which has million rows. It has user id as its primary key. I have an array having 500 user ids in it.
I want to select all the records from the table whose user ids are in the array. I know one method to do this is to change the array into a string and run IN query by passing the string.
But I think it is not the efficient way to do it. So kindly suggest other ways.
I am assuming that your ids are integer. Maybe you are getting this list of Ids from some other sources so that a join on mysql side is not desired solution. If yes, then find the maximum and minimum id present in your 500 Ids list. You can do this in php side. When you have the max and min value, then query mysql db with a where clause
select ...
from table_name
where min_id <= id and id <= max_id
id is the primary key so the advantage is that it is already indexed.
I have done this in the past, I am not sure that my method is the most efficient.
I create a string out of the ids: where id = a or id = b or id = c ...
then I add the select statement in front of it, and do a fetchall.
My guess is that you're getting these user IDs from another table and that you are storing them in an array. If this is correct, then you should change the query that fetches these user IDs so that it uses a join instead.
Joins will help you there, because IN() is not a good programming practice.
You can learn about joins here : http://mysqljoin.com/
I have to select 4 rows randomly from a column.
Is is better to generate randomly 4 id and to perform 4 requests 'select column from database where id = ... '
Or to select all the rows in one request and to choose after?
If you are capable of generating random existing id's, I think the best approach is to use a clause like where id in (id1, id2, id3, id4). This will result in getting 4 records in one query, so no unnecessary query's or records are fetched.
As told before, where id in (id1, id2, id3, id4) is the fastest way from the MySQL perspective. How ever, you will need some logic in the application generating those IDs : All 4 IDs shall exist, be randomly distributed, and you want to avoid duplicates. In worst case you will be retrieving a list of all existend IDs with a huge query, extracting 4 random values, and querying again.
With all that logic to be done, it can be wise to move selection into MySQL:
SELECT * FROM foobar
ORDER BY RAND()
LIMIT 4;
You must understand that this is slow in mysql, but you have a speed gain in the application logic and can be sure to get random values equally seed all over your table.
EDIT:
The comment asks if PHP is fasten in this task then MySQL. Answer is no.
It is not done by "using rand". You need to have an array containing all those IDs in PHP. That is a huge query, lots of TCP traffic, huge array to be buildt in php, huge btree to be buildt by zend engine. Then, with the IDs, you must fire a second query to get the rows for those IDs.
Although the RAND() function may be slow, so far I have not had significant problems with speed. MY strategy is actually to join the database back to a query of itself returning a list of random IDs with a limit.
SELECT *
FROM table AS t1
JOIN (
SELECT rowID
FROM table
ORDER BY RAND()
LIMIT 4
) AS t2
WHERE t1.rowID = t2.rowID
There is also a more robust solution that exist - try checking out this question (asked in 2010).
I would like to select all matches from a commaseparated column in table2, where column could be like this: 0,1,2 OR 2,4,5 OR 2,5 OR 1,3,5 etc.
I have tried with:
SELECT * from table where 1,3,5 IN(SELECT commaseparated FROM table2) WHERE ..
But error on statement when using commas.
I've also tried using REGEXP but in my case i need to search for all matches within 1,3,5
How can i solve this one? :)
Can't do that in standard SQL. it's
WHERE singlevalue IN (list, of, values)
if you want to compare lists against lists, you should revamp your tables so they're properly normalized. Storing formatted data in a field basically negates the purpose of having a relational database - you can't establish relationships with the data if it's not in a format that allows relationships to be formed.
If those CSV lists were in sub-tables, you could do a very simple JOIN query to meet your specifications.