I have a table called trades and has a field session id. The table has specific rows with a similar session id. This reason some rows have a similar session id is that when a trade is placed, it takes an existing session id.
I now want to select rows with similar sessions ids and do something with it.
This is my first query that lists all the rows
SELECT * FROM trades
where trade_session_status="DONE" AND
trade_profit_worker_status="UNDONE"
I have tried this query as well
SELECT * FROM trades
where trade_session_status="DONE" AND
trade_profit_worker_status="UNDONE"
order BY(session_id)
I have looked at the distinct queries and came up with this query
SELECT DISTINCT session_id,id
FROM trades
WHERE trade_session_status="DONE" AND
trade_profit_worker_status="UNDONE"
ORDER BY session_id
The #2 and #3 queries all return the same number of rows. My question is,will the #2 and #3 queries always return the rows with distinct session_id without leaving any rows out?.
Sounds to me that you could use an EXISTS for this.
SELECT *
FROM trades t
WHERE trade_session_status = 'DONE'
AND trade_profit_worker_status = 'UNDONE'
AND EXISTS
(
SELECT 1
FROM trades d
WHERE d.trade_session_status = 'DONE'
AND d.trade_profit_worker_status = 'UNDONE'
AND d.session_id = t.session_id
AND d.id <> t.id
);
Note that the criteria for trade_session_status & trade_profit_worker_status are also used in the query for the EXISTS. I don't know if that's needed for your purpose, so remove them if that's not what you expect. But you get the idea.
Another way is to inner join to a sub-query with the duplicate session_id's.
SELECT t.*
FROM trades t
JOIN
(
SELECT session_id
FROM trades
WHERE trade_session_status = 'DONE'
AND trade_profit_worker_status = 'UNDONE'
GROUP BY session_id
HAVING COUNT(*) > 1
) d ON d.session_id = t.session_id
WHERE t.trade_session_status = 'DONE'
AND t.trade_profit_worker_status = 'UNDONE';
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 have the following 2 queries.
Query 1 :
select distinct(thread_id) from records where client_name='MyClient'
Query 2 :
select max(thread_no) from records
where thread_id='loop_result_from_above_query' AND action='Reviewed'
Is it possible to combine them into a single query ?
The second query is run on every result of the first query.
Thank you.
See attached image of a small snippet of mysql records.
I need a single mysql query to output only records which have action="MyAction" as the latest records for a given set of thread_ids. In the sample data set : record with Sr: 7201
I hope this helps in helping me :)
SELECT client_name, thread_id, MAX(thread_no) max_thread
FROM records
WHERE action='Reviewed' AND client_name='MyClient'
GROUP BY client_name, thread_id
UPDATE 1
SELECT a.*
FROM records a
INNER JOIN
(
SELECT thread_id, max(sr) max_sr
FROM records
GROUP BY thread_id
) b ON a.thread_id = b.thread_id AND
a.sr = b.max_sr
WHERE a.action = 'MyAction'
You can use SELF JOIN, but it is not advisable and will impact your query performance. Please check below query for your reference
SELECT DISTINCT r1.thread_id, MAX(r2.thread_no) from records r1 LEFT JOIN records r2 ON r2.thread_id=r1.thread_id WHERE r1.client_name='MyClient' AND r2.action='Reviewed'
SELECT a.maxthreadid,
b.maxthreadno
FROM (SELECT DISTINCT( thread_id ) AS MaxThreadId
FROM records
WHERE client_name = 'MyClient') a
CROSS JOIN (SELECT Max(thread_no) AS MaxThreadNo
FROM records
WHERE thread_id = 'loop_result_from_above_query'
AND action = 'Reviewed') b
Try this.
SELECT *
FROM (SELECT Row_number()
OVER (
partition BY thread_id
ORDER BY thread_no) no,
Max(thread_no)
OVER(
partition BY thread_id ) Maxthread_no,
thread_id,
action,
client_name
FROM records
Where client_name = 'MyClient') AS T1
WHERE no = 1
AND action = 'Reviewed'
Everything in the following query results in one line for each invBlueprintTypes row with the correct information. But I'm trying to add something to it. See below the codeblock.
Select
blueprintType.typeID,
blueprintType.typeName Blueprint,
productType.typeID,
productType.typeName Item,
productType.portionSize,
blueprintType.basePrice * 0.9 As bpoPrice,
productGroup.groupName ItemGroup,
productCategory.categoryName ItemCategory,
blueprints.productionTime,
blueprints.techLevel,
blueprints.researchProductivityTime,
blueprints.researchMaterialTime,
blueprints.researchCopyTime,
blueprints.researchTechTime,
blueprints.productivityModifier,
blueprints.materialModifier,
blueprints.wasteFactor,
blueprints.maxProductionLimit,
blueprints.blueprintTypeID
From
invBlueprintTypes As blueprints
Inner Join invTypes As blueprintType On blueprints.blueprintTypeID = blueprintType.typeID
Inner Join invTypes As productType On blueprints.productTypeID = productType.typeID
Inner Join invGroups As productGroup On productType.groupID = productGroup.groupID
Inner Join invCategories As productCategory On productGroup.categoryID = productCategory.categoryID
Where
blueprints.techLevel = 1 And
blueprintType.published = 1 And
productType.marketGroupID Is Not Null And
blueprintType.basePrice > 0
So what I need to get in here is the following table with the columns below it so I can use the values timestamp and sort the entire result by profitHour
tablename: invBlueprintTypesPrices
columns: blueprintTypeID, timestamp, profitHour
I need this information with the following select in mind. Using a select to show my intention of the JOIN/in-query select or whatever that can do this.
SELECT * FROM invBlueprintTypesPrices
WHERE blueprintTypeID = blueprintType.typeID
ORDER BY timestamp DESC LIMIT 1
And I need the main row from table invBlueprintTypes to still show even if there is no result from the invBlueprintTypesPrices. The LIMIT 1 is because I want the newest row possible, but deleting the older data is not a option since history is needed.
If I've understood correctly I think I need a subquery select, but how to do that? I've tired adding the exact query that is above with a AS blueprintPrices after the query's closing ), but did not work with a error with the
WHERE blueprintTypeID = blueprintType.typeID
part being the focus of the error. I have no idea why. Anyone who can solve this?
You'll need to use a LEFT JOIN to check for NULL values in invBlueprintTypesPrices. To mimic the LIMIT 1 per TypeId, you can use the MAX() or to truly make sure you only return a single record, use a row number -- this depends on whether you can have multiple max time stamps for each type id. Assuming not, then this should be close:
Select
...
From
invBlueprintTypes As blueprints
Inner Join invTypes As blueprintType On blueprints.blueprintTypeID = blueprintType.typeID
Inner Join invTypes As productType On blueprints.productTypeID = productType.typeID
Inner Join invGroups As productGroup On productType.groupID = productGroup.groupID
Inner Join invCategories As productCategory On productGroup.categoryID = productCategory.categoryID
Left Join (
SELECT MAX(TimeStamp) MaxTime, TypeId
FROM invBlueprintTypesPrices
GROUP BY TypeId
) blueprintTypePrice On blueprints.blueprintTypeID = blueprintTypePrice.typeID
Left Join invBlueprintTypesPrices blueprintTypePrices On
blueprintTypePrice.TypeId = blueprintTypePrices.TypeId AND
blueprintTypePrice.MaxTime = blueprintTypePrices.TimeStamp
Where
blueprints.techLevel = 1 And
blueprintType.published = 1 And
productType.marketGroupID Is Not Null And
blueprintType.basePrice > 0
Order By
blueprintTypePrices.profitHour
Assuming you might have the same max time stamp with 2 different records, replace the 2 left joins above with something similar to this getting the row number:
Left Join (
SELECT #rn:=IF(#prevTypeId=TypeId,#rn+1,1) rn,
TimeStamp,
TypeId,
profitHour,
#prevTypeId:=TypeId
FROM (SELECT *
FROM invBlueprintTypesPrices
ORDER BY TypeId, TimeStamp DESC) t
JOIN (SELECT #rn:=0) t2
) blueprintTypePrices On blueprints.blueprintTypeID = blueprintTypePrices.typeID AND blueprintTypePrices.rn=1
You don't say where you are putting the subquery. If in the select clause, then you have a problem because you are returning more than one value.
You can't put this into the from clause directly, because you have a correlated subquery (not allowed).
Instead, you can put it in like this:
from . . .
(select *
from invBLueprintTypesPrices ibptp
where ibtp.timestamp = (select ibptp2.timestamp
from invBLueprintTypesPrices ibptp2
where ibptp.blueprintTypeId = ibptp2.blueprintTypeId
order by timestamp desc
limit 1
)
) ibptp
on ibptp.blueprintTypeId = blueprintType.TypeID
This identifies the most recent records for all the blueprintTypeids in the subquery. It then joins in the one that matches.
What I want to do is to set every patient its unique patient code which starts with 1 and it's not based on row id. Id only specifies order. Something like this:
patient_id patient_code
2 1
3 2
4 3
This is my query:
UPDATE patients p1
SET p1.patient_code = (
SELECT COUNT( * )
FROM patients p2
WHERE p2.patient_id <= p1.patient_id
)
But it is throwing error:
#1093 - You can't specify target table 'p1' for update in FROM clause
I found this thread: Mysql error 1093 - Can't specify target table for update in FROM clause.But I don't know how to apply approved answer this to work with subquery WHERE which is necessary for COUNT.
UPDATE
patients AS p
JOIN
( SELECT
p1.patient_id
, COUNT(*) AS cnt
FROM
patients AS p1
JOIN
patients AS p2
ON p2.patient_id <= p1.patient_id
GROUP BY
p1.patient_id
) AS g
ON g.patient_id = p.patient_id
SET
p.patient_code = g.cnt ;
I found working solution, but this is just workaround:
SET #code=0;
UPDATE patients SET patient_code = (SELECT #code:=#code+1 AS code)
Try this,
UPDATE patients p1 INNER JOIN
(
SELECT COUNT(*) as count,patient_id
FROM patients
group by patient_id
)p2
SET p1.patient_code=p2.count
WHERE p2.patient_id <= p1.patient_id
SQL_LIVE_DEMO
Thanks to Mari's answer I found a solution to my similar problem. But I wanted to add a bit of an explanation which for me at first wasn't too clear from his answer.
What I wanted to do would have been as simple as the following:
UPDATE my_comments AS c
SET c.comment_responses = (
SELECT COUNT(c1.*) FROM my_comments AS c1
WHERE c.uid = c.parent_uid
);
Thanks to Mari I then found the solution on how to achieve this without running into the error You can't specify target table 'p1' for update in FROM clause:
UPDATE my_comments AS c
INNER JOIN (
SELECT c1.parent_uid, COUNT(*) AS cnt
FROM my_comments AS c1
WHERE c1.parent_uid <> 0
GROUP BY c1.parent_uid
) AS c2
SET c.comment_responses = c2.cnt
WHERE c2.parent_uid = c.uid;
My problems before getting to this solution were 2:
the parent_uid field doesn't always contain an id of a parent which is why I added the WHERE statement in the inner join
I didn't quite understand why I would need the GROUP BY until I executed the SELECT statement on it's own and the answer is: because COUNT groups the result and really counts everything. In order to prevent this behavior the GROUP BY is needed. In my case I didn't have to group it by uid though but the parent_uid to get the correct count. If I grouped it by uid the COUNT would always be 1 but the parent_uid existed multiple times in the result. I suggest you check the SELECT statement on it's own to check if it's the result you expect before you execute the full UPDATE statement.
I have two tables(Friends and News_Feed). I need to retrieve the most recent rows(highest id) from the News_Feed table. The catch is that I only want to select rows in the News_Feed table that pertain to either of the two columns in the Friends table. I also need to order by News_Feed.id, so creating two queries(such as first selecting my friends, and then looping into a News_Feed query) will not work. Tables are set up as follows:
-Friends-
id
user
user_friending
News_Feed
id
pertaining_user
action
orig_comment
My current, unworking query, is...
$result = mysql_query("SELECT * FROM News_Feed WHERE pertaining_user=(SELECT user FROM Friends WHERE user_friending='37' AND is_confirmed='1' UNION SELECT user_friending FROM Friends WHERE user='37' AND is_confirmed='1') AND orig_comment='0' ORDER BY id DESC")or die(mysql_error());
while($row_news = mysql_fetch_array($result)){
This returns subquery returns more than one row error, which I understand. There must be way though to do this.
Use exists:
select
*
from
News_Feed f
where
exists (
select
1
from
friends u
where
(u.user = f.pertaining_user and u.user_friending = '37')
or (u.user_friending = f.pertaining_user and u.user = '37')
and u.is_confirmed = 1
)
order by
f.id desc
This will be much faster than trying to do an in with a union. It does a semi-join and throws out invalid rows immediately.
You are probably looking for the IN keyword.
SELECT *
FROM News_Feed
WHERE pertaining_user IN
(
SELECT user
FROM Friends
WHERE user_friending='37'
AND is_confirmed='1'
UNION
SELECT user_friending
FROM Friends
WHERE user='37'
AND is_confirmed='1')
AND orig_comment='0'
ORDER BY id DESC