The following query returns 2303 rows:
SELECT a.*
FROM cur_analises a
INNER JOIN cur_materias_subsidiarias ms
ON ms.materia_id = a.materia_id
AND ms.subsidiaria_id IN(SELECT id FROM cur_subsidiarias WHERE cliente_id = 134)
INNER JOIN cur_materias m
ON m.id = a.materia_id
INNER JOIN cur_clientes c
ON c.carga_id = ms.subsidiaria_id
WHERE a.cliente_id = 134;
I need to update the cliente_id field of all those 2303 rows from table cur_analises with the value from cur_clientes.id. However, when I try to turn that SELECT query into the following UPDATE, it only affects 2297 rows, according to MySQL Workbench:
UPDATE cur_analises a
INNER JOIN cur_materias_subsidiarias ms
ON ms.materia_id = a.materia_id
AND ms.subsidiaria_id IN(SELECT id FROM cur_subsidiarias WHERE cliente_id = 134)
INNER JOIN cur_materias m
ON m.id = a.materia_id
INNER JOIN cur_clientes c
ON c.carga_id = ms.subsidiaria_id
SET a.cliente_id = c.id
WHERE a.cliente_id = 134;
I have no idea why it's missing 6 rows. What am I doing wrong?
You are probably not joining on a unique value or set of values at some point in the query causing denormalization of your result set. Then when you do the update it only updates the rows that actually meet the criteria of the joins for the table aliased as a. Only you can know what are truly non denormalizing joins in your query and fix them.
We had a similar case, the issue was with mysql partitioning. Once we revert partitioning everything is ok again.
Related
Without going into the details of the tables, here is a query that outputs 34 rows.
SELECT `t`.`id_product`,
`product_lang`.`name`,
supplies_detail.id_supplies_detail,
`supplies_in_process`.id_supply
FROM `ps_product` `t`
LEFT OUTER JOIN `ps_product_lang` `product_lang` ON (`product_lang`.`id_product` = `t`.`id_product`)
LEFT OUTER JOIN `supplies_detail` `supplies_detail` ON (`supplies_detail`.`id_product` = `t`.`id_product`)
LEFT OUTER JOIN `supplies` `supplies_in_process`
ON (`supplies_detail`.`id_supply` = `supplies_in_process`.`id_supply`) AND
(supplies_in_process.state = 'added')
WHERE ((product_lang.name NOT LIKE '[del]%') AND (t.group_id = '14884'))
ORDER BY t.id_product DESC;
Query without GROUP BY
But it is important for the processor to understand that there will be no rows with duplicate t.id_product in the result, so we add GROUP BY t.id_product to this query.
The result changes to:
Query with GROUP BY
With exactly the same 34 rows we get additional unrelated data. How did it happen?
Thanks
MySQL 8.0.25-15
I have the following query:
SELECT PKID, QuestionText, Type
FROM Questions
WHERE PKID IN (
SELECT FirstQuestion
FROM Batch
WHERE BatchNumber IN (
SELECT BatchNumber
FROM User
WHERE RandomString = '$key'
)
)
I've heard that sub-queries are inefficient and that joins are preferred. I can't find anything explaining how to convert a 3+ tier sub-query to join notation, however, and can't get my head around it.
Can anyone explain how to do it?
SELECT DISTINCT a.*
FROM Questions a
INNER JOIN Batch b
ON a.PKID = b.FirstQuestion
INNER JOIN User c
ON b.BatchNumber = c.BatchNumber
WHERE c.RandomString = '$key'
The reason why DISTINCT was specified is because there might be rows that matches to multiple rows on the other tables causing duplicate record on the result. But since you are only interested on records on table Questions, a DISTINCT keyword will suffice.
To further gain more knowledge about joins, kindly visit the link below:
Visual Representation of SQL Joins
Try :
SELECT q.PKID, q.QuestionText, q.Type
FROM Questions q
INNER JOIN Batch b ON q.PKID = b.FirstQuestion
INNER JOIN User u ON u.BatchNumber = q.BatchNumber
WHERE u.RandomString = '$key'
select
q.pkid,
q.questiontext,
q.type
from user u
join batch b
on u.batchnumber = b.batchnumber
join questions q
on b.firstquestion = q.pkid
where u.randomstring = '$key'
Since your WHERE clause filters on the USER table, start with that in the FROM clause. Next, apply your joins backwards.
In order to do this correctly, you need distinct in the subquery. Otherwise, you might multiply rows in the join version:
SELECT q.PKID, q.QuestionText, q.Type
FROM Questions q join
(select distinct FirstQuestion
from Batch b join user u
on b.batchnumber = u.batchnumber and
u.RandomString = '$key'
) fq
on q.pkid = fq.FirstQuestion
As to whether the in or join version is better . . . that depends. In some cases, particularly if the fields are indexed, the in version might be fine.
Im writing this complex query to return a large dataset, which is about 100,000 records. The query runs fine until i add in this OR statement to the WHERE clause:
AND (responses.StrategyFk = strategies.Id Or responses.StrategyFk IS
Null)
Now i understand that by putting the or statement in there it adds a lot of overhead.
Without that statement and just:
AND responses.StrategyFk = strategies.Id
The query runs within 15 seconds, but doesn't return any records that didn't have a fk linking a strategie.
Although i would like these records as well. Is there an easier way to find both records with a simple where statement? I can't just add another AND statement for null records because that will break the previous statement. Kind of unsure of where to go from here.
Heres the lower half of my query.
FROM
responses, subtestinstances, students, schools, items,
strategies, subtests
WHERE
subtestinstances.Id = responses.SubtestInstanceFk
AND subtestinstances.StudentFk = students.Id
AND students.SchoolFk = schools.Id
AND responses.ItemFk = items.Id
AND (responses.StrategyFk = strategies.Id Or responses.StrategyFk IS Null)
AND subtests.Id = subtestinstances.SubtestFk
try:
SELECT ... FROM
responses
JOIN subtestinstances ON subtestinstances.Id = responses.SubtestInstanceFk
JOIN students ON subtestinstances.StudentFk = students.Id
JOIN schools ON students.SchoolFk = schools.Id
JOIN items ON responses.ItemFk = items.Id
JOIN subtests ON subtests.Id = subtestinstances.SubtestFk
LEFT JOIN strategies ON responses.StrategyFk = strategies.Id
That's it. No OR condition is really needed, because that's what a LEFT JOIN does in this case. Anywhere responses.StrategyFk IS NULL will result in no match to the strategies table, and it wil return a row for that.
See this link for a simple explanation of joins: http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html
After that, if you're still having performance issues then you can start looking at the EXPLAIN SELECT ... ; output and looking for indexes that may need to be added. Optimizing Queries With Explain -- MySQL Manual
Try using explicit JOINs:
...
FROM responses a
INNER JOIN subtestinstances b
ON b.id = a.subtestinstancefk
INNER JOIN students c
ON c.id = b.studentfk
INNER JOIN schools d
ON d.id = c.schoolfk
INNER JOIN items e
ON e.id = a.itemfk
INNER JOIN subtests f
ON f.id = b.subtestfk
LEFT JOIN strategies g
ON g.id = a.strategyfk
Im trying to make a a query, but its doubling the Sum values
SELECT
cidades.id AS id,
cidades.name AS municipio,
Sum(conjuntos.n_uhs) AS uh,
programas.id AS programa,
conjuntos.name
FROM
conjuntos
Inner Join conjuntos_programas ON conjuntos_programas.conjunto_id = conjuntos.id
Inner Join programas ON programas.id = conjuntos_programas.programa_id
Inner Join cidades ON conjuntos.cidade_id = cidades.id
WHERE
conjuntos.situation_id = 2
GROUP BY
conjuntos.cidade_id
ORDER BY
municipio ASC
You've got duplicate rows, you can check this by removing the group by and the SUM(... from your query.
Change the query as follows and tell me if that fixes to problem.
SELECT DISTINCT
cidades.id AS id,
cidades.name AS municipio,
SUM(conjuntos.n_uhs) AS uh,
programas.id AS programa,
conjuntos.name
FROM conjuntos
INNER JOIN conjuntos_programas ON conjuntos_programas.conjunto_id = conjuntos.id
INNER JOIN programas ON programas.id = conjuntos_programas.programa_id
INNER JOIN cidades ON conjuntos.cidade_id = cidades.id
WHERE conjuntos.situation_id = 2
GROUP BY conjuntos.cidade_id
ORDER BY municipio ASC
It sounds like you have a one to many relationship between two or more of your tables to be doing this. Try doing a SELECT * and start debugging your query to see where it is duplicating the rows.
I am trying to update a field in my table based on if it exists in two join tables.
update quotes
inner join collection_records ON quotes.id <> collection_records.record_id
inner join subcollection_records ON quotes.id <> subcollection_records.record_id
set quotes.status_id = 1
where collection_records.type = 'Quote'
or subcollection_records.type = 'Quote'
this query runs, but hangs. If I remove on inner join it works, but I need to check both join tables for the existance of the quote id.
Have to be careful, because using JOINs risks duplicated data for the sake of the unique supporting data. I re-wrote your query as:
UPDATE QUOTES
SET status_id = 1
WHERE id NOT IN (SELECT cr.record_id
FROM COLLECTION_RECORDS cr
WHERE cr.type = 'Quote')
AND id NOT IN (SELECT sr.record_id
FROM SUBCOLLECTION_RECORDS sr
WHERE sr.type = 'Quote')
Using LEFT JOIN/IS NULL:
UPDATE QUOTES
LEFT JOIN COLLECTION_RECORDS cr ON cr.record_id = id
AND cr.type = 'Quote'
LEFT JOIN SUBCOLLECTION_RECORDS sr ON sr.record_id = id
AND sr.type = 'Quote'
SET status_id = 1
WHERE cr.record_id IS NULL
AND sr.record_id IS NULL
My guess is that it's mainly due to the <> (NOT EQUALS) operator. Is that really what you're looking for here?
Also, if you have a Quote record in both the joinging tables....you will get 2 records back. Seems that taking one of the joins out returns only one record to you. Try doing a select instead of the update on a certain Quote that exists in both tables and see if you get two records back. You will have to modify the joins down in order to get one quote record returned.