I have a query that returns a bunch of information and using a join to join two tables and it works perfectly fine.
But I have a field called tickets which I need to see if there is a time available and if there is even one set it to 1 otherwise set it to 0. So like this.
SELECT
name,poster,sid,tickets = (IF SELECT id FROM times WHERE shows.tid=times.tid LIMIT 1,
if value returned set to 1, otherwise set to 0)
FROM shows JOIN show_info ON (id) WHERE sid=54 order by name ASC
Obviously that is not a correct MySQL statement, but it would give an example of what I am looking for.
Is this possible? Or do I need to do the first select then for a loop through results and do the second select and set value that way? Or is one better performance wise?
I would look at EXISTS it is in most of the cases much faster then to COUNT all the items that matches your where statement. With that said. You query should look something like this:
SELECT
name,
poster,
sid,
(
CASE WHEN EXISTS(SELECT NULL FROM times WHERE shows.tid=times.tid)
THEN 1
ELSE 0
END
)AS tickets
FROM
shows
JOIN show_info ON (id) WHERE sid=54 order by name ASC
Look at CASE statement
SELECT name,poster,sid,
Case WHEN (SELECT count(id) FROM times WHERE shows.tid=times.tid) > 0 THEN 1 else 0 END as Tickets
FROM shows
JOIN show_info ON (id)
WHERE sid=54 order by name ASC
try
SELECT
name,
poster,
sid,
CASE WHEN (SELECT COUNT(*) FROM times WHERE shows.tid=times.tid ) > 0 THEN 1 ELSE 0 END CASE tickets
FROM shows
JOIN show_info ON (id)
WHERE sid=54
order by name ASC
For reference on CASE see MySQL Docs.
This is the simplest way to do this I can think of:
SELECT name, poster, sid,EXISTS(SELECT * times WHERE shows.tid=times.tid) tickets
FROM shows
JOIN show_info USING (id)
WHERE sid = 54
ORDER BY name
Related
I have a query like this . I have compound index for CC.key1,CC.key2.
I am executing this in a big database
Select * from CC where
( (
(select count(*) from Service s
where CC.key1=s.sr2 and CC.key2=s.sr1) > 2
AND
CC.key3='new'
)
OR
(
(select count(*) from Service s
where CC.key1=s.sr2 and CC.key2=s.sr1) <= 2
)
)
limit 10000;
I tried to make it as inner join , but its getting slower . How can i optimize this query ?
The trick here is being able to articulate a query for the problem:
SELECT *
FROM CC t1
INNER JOIN
(
SELECT cc.key1, cc.key2
FROM CC cc
LEFT JOIN Service s
ON cc.key1 = s.sr2 AND
cc.key2 = s.sr1
GROUP BY cc.key1, cc.key2
HAVING COUNT(*) <= 2 OR
SUM(CASE WHEN cc.key = 'new' THEN 1 ELSE 0 END) > 2
) t2
ON t1.key1 = t2.key1 AND
t1.key2 = t2.key2
Explanation:
Your original two subqueries would only add to the count if a given record in CC, with a given key1 and key2 value, matched to a corresponding record in the Service table. The strategy behind my inner query is to use GROUP BY to count the number of times that this happens, and use this instead of your subqueries. The first count condition is your bottom subquery, and the second one is the top.
The inner query finds all key1, key2 pairs in CC corresponding to records which should be retained. And recognize that these two columns are the only criteria in your original query for determining whether a record from CC gets retained. Then, this inner query can be inner joined to CC again to get your final result set.
In terms of performance, even this answer could leave something to be desired, but it should be better than a massive correlated subquery, which is what you had.
Basically get the Columns that must not have a duplicate then join them together. Example:
select *
FROM Table_X A
WHERE exists (SELECT 1
FROM Table_X B
WHERE 1=1
and a.SHOULD_BE_UNIQUE = b.SHOULD_BE_UNIQUE
and a.SHOULD_BE_UNIQUE2 = b.SHOULD_BE_UNIQUE2
/* excluded because these columns are null or can be Duplicated*/
--and a.GENERIC_COLUMN = b.GENERIC_COLUMN
--and a.GENERIC_COLUMN2 = b.GENERIC_COLUMN2
--and a.NULL_COLUMN = b.NULL_COLUMN
--and a.NULL_COLUMN2 = b.NULL_COLUMN2
and b.rowid > a.ROWID);
Where SHOULD_BE_UNIQUE and SHOULD_BE_UNIQUE2 are columns that shouldn't be repeated and have unique columns and the GENERIC_COLUMN and NULL_COLUMNS can be ignored so just leave them out of the query.
Been using this approach when we have issues in Duplicate Records.
With the limited information you've given us, this could be a rewrite using 'simplified' logic:
SEELCT *
FROM CC NATURAL JOIN
( SELECT key1, key2, COUNT(*) AS tally
FROM Service
GROUP
BY key1, key2 ) AS t
WHERE key3 = 'new' OR tally <= 2;
Not sure whether it will perform better but might give you some ideas of what to try next?
i am running this query, witch consists of 3 recursive selects.
select idigorUserFields
from ( select *
from ( select *
from igorUserFields f
where f.idigorUsers = 1
order by f.idigorUserFields desc) tbl
group by tbl.idigorUserFieldTemplates ) tbl2
where value="qf" and idigorUserFields = 28
what I am trying to do is simple:
get all fields, order by insert date ( i am using primary key for that )
get the last inserted value for a field (idigorFieldTemplates)
compare the last inserted field with the one i am about to insert, to save some space on the database
some relevant info:
idigorUserFieldTemplates is the primary key for a "html user fields table"
the last inserted value is the one displayed on the program
also, I have a sqlfiddle! with some data to test.
my question is: can I make this query better? and what do I need to use to do that.
Alright so it looks like you want to get the last inserted value for a given user and value and then compare that with the data you are about to insert. Here's how I would tackle that
SELECT a.idigorUserFieldTemplates
FROM igorUserFields AS a
INNER JOIN (SELECT MAX(idigorUserFields) as max_id FROM igorUserFields WHERE idigorUsers = 1 AND value="qf") AS b
ON a.idigorUserFields= b.max_id
The subquery is giving me the largest idigorUserFields for which idigorUsers = 1 AND value="qf." For this to work, you have to assume that that the primary key (idigorUserFields) is incrementing with date. You indicated in your post that it does, so hopefully this assumption is okay.
Once we've got that last updated record, we then join back with igorUserFields to get the corresponding value of idigorUserFieldTemplates
edit:
I want to get the last inserted for a given user and field. then compare it with what i am about to insert.
I am sorry if I was not clear enough about what I wanted.
I modified the above sql and i got what i wanted:
SELECT a.* FROM igorUserFields
AS a INNER JOIN
(SELECT MAX(idigorUserFields) as max_id
FROM igorUserFields WHERE idigorUsers = 1 and idigorUserFieldTemplates =6) AS b
ON a.idigorUserFields= b.max_id
AND value="qf"
thanks! now I got a more efficient solution :)
if all you want is the largest id by specific data just specify that order it and limit it like so
SELECT idigorUserFields
FROM igorUserFields
WHERE idigorUsers = 1 AND value="qf"
ORDER BY idigorUserFields DESC
LIMIT 1
DEMO
if you are trying to get the last inserted value then you can get the largest idigorUserFields assuming its auto incremented.
SELECT MAX(idigorUserFields) FROM idigorUserFields
and then if you want a specific column from that field you could use it as a subquery
SELECT f.idigorUserFieldTemplates
FROM idigorUserFields f
WHERE f.idigorUserFields =
( SELECT MAX(idigorUserFields)
FROM idigorUserFields
WHERE idigorUsers = 1 AND value="qf"
)
I have a complicated query that boils down to this:
UPDATE usertable
SET userstatus =
(SELECT numposts*5 as status FROM
(SELECT count(*) as numposts FROM poststable WHERE poststable.userid = usertable.userid) as table2
)
WHERE usertable.userid > 0
It's a query that updates every user record and sets the user's status to some calculated value based on the number of rows in a child table.
The problem is that usertable.userid does not make it down to the second level subquery.
The query works when presented like this, with only one level down:
UPDATE usertable
SET userstatus =
(SELECT count(*) as numposts FROM poststable WHERE poststable.userid = usertable.userid)
WHERE usertable.userid > 0
The problem is that the calculation query in the real situation is very complicated.
The question is: is there a way I can get a 2nd level subquery to recognize a value from the top level query? In this example, is there a way to get usertable.userid recognized 2 levels down?
Thanks!
-Nico
Instead of doing a correlated subquery row by row, I would generate a derived table as a one-time subquery for all userid's, then join that to the table you want to update. MySQL supports multi-table update syntax:
UPDATE usertable AS u
LEFT OUTER JOIN (
SELECT userid, COUNT(*) AS numposts
FROM poststable
GROUP BY userid
ORDER BY NULL
) AS t USING (userid)
SET u.userstatus = 5 * COALESCE(t.numposts, 0)
WHERE u.userid > 0
I know you said your real query is more complex, but the same principle may solve it.
I'm sure this will be quite simple for some one clued up in SQL but I think it needs a sub query or something. I have a table which basically has a load of order numbers in it and a reply column from an XML API. Either FAIL or SUCCESS.
A brand new row is inserted into the DB after every request. So there may be 5 FAILS for one order number, and on the 6th attempt a record is inserted saying SUCCESS.
How can I put out order numbers that ONLY have a FAIL status next to them?
This will allow me to figure out what records need looking into that continuously fail in the API request.
Try this, by grouping your orders with primary key (order_id)
SELECT * FROM
(
SELECT GROUP_CONCAT(status) as status_combined, order_id
FROM orders
GROUP BY order_id
) AS order_tmp
WHERE status_combined NOT LIKE '%SUCCESS%'
Edit (As per asker comments)
SELECT * FROM
(
SELECT GROUP_CONCAT(status) as status_combined, order_id
FROM orders
JOIN certificates ON certificates.Ordernumber = orders.OrderNumber
GROUP BY order_id
) AS order_tmp
WHERE status_combined NOT LIKE '%SUCCESS%'
please make sure you need to join based on "Ordernumber" or "order_id"
Try this
select m.*
from Main m
join Transactiontable tt
on m.orderid = tt.orderid
group by tt.status , m.orderid
having count(case when tt.status = "failed") = count(tt.status)
You can use simple sql query using a where clause:
select *
from some_table
where Column_From_some_table_has_value = your_particular_value
thats enough.
You can have a look at How to use where clause in sql
Thanks
This is probably the cleanest way to do it:
select *
from mytable
where id in (
select id
from mytable
group by id
having sum(status = 'SUCCESS') = 0)
I'm not a fan of #Minesh's answer because it uses both an aggregate function and the LIKE operator. Both of those can cause performance issues since there won't be any indexes to help the query out with the difficult part of the work. The LIKE clause particularly is a lot of work for the database since it will need to scan every result.
I'm more familiar with SQL Server, but this should work well for you:
SELECT *
FROM Orders
WHERE OrderNumber NOT IN (
SELECT OrderNumber
FROM Orders
WHERE Status = 'SUCCESS')
AND OrderNumber NOT IN (
SELECT OrderNumber
FROM Certificates
WHERE OrderStatus = 'CANCELLED')
I have a working query that will return some results(records) from my database, like:
123|John Williams|IL|M|06/01/2011|ACTIVE
124|Mary Haque|NY|F|TERMINATED|06/30/2011
124|Mary Haque|NY|F|07/01/2011|ACTIVE
125|Alex Chan|VA|07/01/2011|ACTIVE
126|Rob Kreb|VA|TERMINATED|06/20/2011
As you can see, the result is simply a list of customer records, while the last two fields indicate whether the member is active or terminated and associated active/terminated date.
The complication now is, as you can see for member with ID 124 (Mary Haque), she has two records, and for this kind of two-record customer, I only want to keep the row where the member is active while totally ignore her terminated history. So for example, the desired output for the above should be:
123|John Williams|IL|M|06/01/2011|ACTIVE
124|Mary Haque|NY|F|07/01/2011|ACTIVE
125|Alex Chan|VA|07/01/2011|ACTIVE
126|Rob Kreb|VA|TERMINATED|06/20/2011
as you can see, now Mary Haque only has her active information on the result. The above result is generate by a SQL "Select" query, but I couldn't simply append a "WHERE status=ACTIVE" to this query because I still want to keep the members that only has ONE record like Rob Kreb above even though he is terminated. I only want the filtering for TERMINATED member record to take place when a certain member has two records.
FYI, my current query looks like this:
SELECT * FROM customer_change WHERE CUSTOMER_LOGIN NOT IN(SELECT CUSTOMER_LOGIN FROM customer_full WHERE CUSTOMER_LOGIN IS NOT NULL)
UNION
SELECT * FROM customer_change WHERE CUSTOMER_POINTS=0 AND CUSTOMER_LOGIN NOT IN(SELECT CUSTOMER_LOGIN FROM customer_full WHERE CUSTOMER_POINTS=0 AND CUSTOMER_LOGIN IS NOT NULL)
Thanks for the help in advance!
colX and colY are the last 2 columns of the query:
SELECT *
FROM (your_UNION_query) AS p
WHERE NOT ( colX = 'TERMINATED'
AND EXISTS
( SELECT *
FROM (your_UNION_query) AS q
WHERE q.id = p.id
AND q.colY = 'ACTIVE'
)
)
Something like this will do the trick:
DELETE
FROM tablename
WHERE tablename.status = 'TERMINATED'
AND tablename.id IN(SELECT
id
FROM (SELECT
t.id
FROM tablename t
GROUP BY t.id
HAVING COUNT(t.id) > 1) AS T1)
Assuming that id is the field refering to 124,125, etc.