I have a problem. I want to use subquery tm in LEFT JOIN .. ON
SELECT t.*,
(SELECT `uid` FROM `truck_transport` tm WHERE tm.from = t.station ORDER BY RAND() LIMIT 1) as tm
FROM `truck_trailer` t
LEFT JOIN `truck_transport` tm2 ON (tm2.uid = tm) ...
If I use subquery in FROM result of rand is always the same.
Sorry for my language :/
try this
SELECT t.*, tm.uid
FROM `truck_trailer` t
LEFT JOIN (SELECT `uid` FROM `truck_transport` ORDER BY RAND() LIMIT 1) as tm
ON (tm.uid = t.station)
mynawaz has written a correct query.
Your subquery will always return only one result because of limit 1. If you want only one result to come then use JOIN instead of LEFT JOIN. because left join table always returns matching rows and non matching with NULL of right side table.
Related
What I am trying to do it with below code, getting all keywords with their positions via LEFT JOIN, it works fine but it shows the first position of each keyword, but I want to show the last position that recorded (by date).
SELECT keyword.id, keyword.title, keyword.date, rank.position FROM keyword
LEFT JOIN rank
ON rank.wordid = keyword.id
GROUP BY keyword.id
ORDER BY keyword.date DESC
How can I do this? Should I use subquery or what? Is there any way to do this without a subquery?
SAMPLE DATA
What I want:
Get 17 instead of 13, I mean last record of position.
Do not use group by for this! You want to filter, so use a where clause. In this case, using a correlated subquery works well:
SELECT k.id, k.title, k.date, r.position
FROM keyword k LEFT JOIN
rank r
ON r.wordid = k.id AND
r.date = (SELECT MAX(r2.date)
FROM rank r2
WHERE r2.wordid = k.id
)
ORDER BY k.date DESC
You can use below query
SELECT keyword.id, keyword.title, keyword.date, rankNew.position FROM keyword LEFT JOIN (
SELECT rank.wordid, rank.position FROM rank ORDER BY rank.id DESC LIMIT 0, 1) AS rankNew ON (rankNew.wordid = keyword.id);
You can get more reference from Retrieving the last record in each group - MySQL
How to fetch rows where a joined subquery is null?
SELECT *
FROM bank_recon b
LEFT JOIN (
SELECT o.bank_recon_id
FROM data_voucher_ocr_bank o
LEFT JOIN data_voucher v ON v.id=o.data_voucher_id
WHERE v.is_ocr_verified=1
LIMIT 1
) s ON s.bank_recon_id=b.id
WHERE s IS NULL
update
When using this query (the subquery) something is fetched depending on if is_ocr_verified is set or not
SELECT o.bank_recon_id
FROM data_voucher_ocr_bank o
LEFT JOIN data_voucher v ON v.id=o.data_voucher_id
WHERE v.is_ocr_verified=1 && o.bank_recon_id=320062
When using this query everything is fetched no matter what!?
SELECT b.txt, b.amount
FROM bank_recon b
LEFT JOIN (
SELECT o.bank_recon_id
FROM data_voucher_ocr_bank o
LEFT JOIN data_voucher v ON v.id=o.data_voucher_id
WHERE v.is_ocr_verified=1
LIMIT 1
) s ON s.bank_recon_id=b.id
WHERE b.id=320062 && s.bank_recon_id IS NULL
Specify a column in your WHERE clause, not just the subquery.
WHERE s.bank_recon_id IS NULL
An anti join (which is what you are trying to apply here) is a method we use when the straight-forward NOT IN or NOT EXISTS have performance issues in a DBMS.
Provided data_voucher_ocr_bank.bank_recon_id cannot be null, we can use:
SELECT txt, amount
FROM bank_recon
WHERE id NOT IN
(
SELECT bank_recon_id
FROM data_voucher_ocr_bank
WHERE data_voucher_id IN (SELECT id FROM data_voucher WHERE is_ocr_verified = 1)
);
(Otherwise we'd add AND bank_recon_id IS NOT NULL or use NOT EXISTS instead.)
I'm trying to left join the second table useri_ban based on the users' ids, with the extra condition: useri_ban.start_ban = max_start.
In order for me to calculate max_start, I have to run the following subquery:
(SELECT MAX(ub.start_ban) AS max_start, user_id FROM useri_ban ub WHERE ub.user_id = useri.id)
Furthermore, in order to add max_start to every row, I need to inner join this subquery's result into the main result. However, it seems that once I apply that join, the subquery is no longer able to access useri.id.
What am I doing wrong?
SELECT
useri.id as id,
useri.email as email,
useri_ban.warning_type_id as warning_type_id,
useri_ban.type as type,
useri.created_at AS created_at
FROM `useri`
inner join
(SELECT MAX(ub.start_ban) AS max_start, user_id FROM useri_ban ub WHERE ub.user_id = useri.id) `temp`
on `useri`.`id` = `temp`.`user_id`
left join `useri_ban` on `useri_ban`.`user_id` = `useri`.`id` and `useri_ban`.`start_ban` = `max_start`
Does this solve your problem? You need GROUP BY in the inner query instead of another join.
SELECT useri.id, useri.email, maxQuery.maxStartBan
FROM useri
INNER JOIN
(
SELECT useri_ban.user_id ubid, MAX(useri_ban.startban) maxStartBan
FROM useri_ban
GROUP BY useri_ban.user_id
) AS maxQuery
ON maxQuery.ubid = useri.id;
I am trying to select items that doesn't have a specific value in another table, I was able to achieve the result that I wanted by using a subquery, however it's very slow so I am wondering if I could do it differently...
SELECT
content.*,
(SELECT views
FROM content_views
WHERE content_views.content = content.record_num
) as views
FROM content
RIGHT JOIN watch_log ON content.record_num = watch_log.content
WHERE content.enabled = 1
AND 24 NOT IN
(SELECT niche
FROM content_niches
WHERE content_niches.content = content.record_num
)
ORDER BY content.encoded_date
DESC LIMIT 0,6
I tried using a LEFT OUTER JOIN, but couldn't get the same result...
SELECT
content.*,
(SELECT content_views.views
FROM content_views
WHERE content_views.content = content.record_num
) as views
FROM content
RIGHT JOIN watch_log ON content.record_num = watch_log.content
LEFT OUTER JOIN content_niches ON content.record_num = content_niches.content AND content_niches.niche = 24
WHERE content.enabled = 1
ORDER BY content.encoded_date
DESC LIMIT 0,6
Mixing left and right outer joins is just confusing. In fact, right join isn't really needed. It can usually be replaced by left join. In your case, it can be replaced by inner join, because the where clause turns it into an inner join. So, how about:
SELECT c.*,
(SELECT views
FROM content_views cv
WHERE cv.content = c.record_num
) as views
FROM content c JOIN
watch_log wl
ON c.record_num = wl.content
WHERE c.enabled = 1 AND
NOT EXISTS (SELECT 1
FROM content_niches cn
WHERE cn.content = c.record_num AND
cn.niche = 24
)
ORDER BY c.encoded_date DESC
LIMIT 0, 6;
For performance you want indexes: content(enabled, encoded_date, record_num), content_views(content, views), and content_niches(content, niche).
Notes:
Don't mix different types of outer joins, unless you really, really understand what they are doing.
Use table aliases that abbreviations of the table names. This makes queries easier to write and to read.
Whatever your preference for formatting, don't start a line in a query with DESC (or ASC); this is a modifier on ORDER BY.
NOT EXISTS is better than NOT IN. The former handles NULL values the way you would expect. The latter returns nothing if there are NULL values.
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.