How to combine GROUP BY and JOIN statements in MySQL? - mysql

I am trying to combine a query I have run on one table with some columns on another table. The query I ran calculates the total of something for me by this:
SELECT security.Loan_id
, SUM(security.SecMktValue) AS TotalSecMktValue
FROM security
GROUP
BY Loan_id
ORDER
BY loan_id ASC;
I then tried to join this query with columns from another table by:
SELECT loans.Loan_id, loans.TotalLoanAmt
FROM loans
JOIN(SELECT SUM(security.SecMktValue) AS TotalSecMktValue,security.Loan_id
FROM security
GROUP BY Loan_id ASC)
ON loans.Loan_id = security.Loan_id;
However, this wont run as it says there is an error with my SQL syntax even though nothing is underlined in red. Does anyone know why that is?

You're missing an alias:
SELECT loans.Loan_id, loans.TotalLoanAmt
FROM loans
JOIN(
SELECT SUM(security.SecMktValue) AS TotalSecMktValue,security.Loan_id
FROM security
GROUP BY Loan_id ASC
) security -- <-- here
ON loans.Loan_id = security.Loan_id;

MySQL requires an alias to be assigned to the derived table (i.e. a correlation name associated with the inline view). The qualifier security is out of scope outside the inline view i.e. it's not a valid reference in the outer query.)
Here's an example, assigning the alias t to the derived table. Notice that in the outer query, references to columns from the inline view are qualified with t.
SELECT l.loan_id
, l.totalloanamt
, t.totalsecmktvalue
FROM loans l
LEFT
JOIN (
SELECT s.loan_id
, SUM(s.secmktvalue) AS totalsecmktvalue
FROM security s
GROUP
BY s.loan_id
) t
ON t.loan_id = l.loan_id
ORDER
BY l.loan_id

If i got you question right then this should work :)
SELECT security.Loan_id,SUM(security.SecMktValue) AS TotalSecMktValue
FROM security security
JOIN loans loan
ON loans.Loan_id = security.Loan_id
GROUP BY Loan_id ASC

Related

MySQL Inner join naming error?

http://sqlfiddle.com/#!9/e6effb/1
I'm trying to get a top 10 by revenue per brand for France on december.
There are 2 tables (first table has date, second table has brand and I'm trying to join them)
I get this error "FUNCTION db_9_d870e5.SUM does not exist. Check the 'Function Name Parsing and Resolution' section in the Reference Manual"
Is my use of Inner join there correct?
It's because you had an extra space after SUM. Please change it from
SUM (o1.total_net_revenue)to SUM(o1.total_net_revenue).
See more about it here.
Also after correcting it, your query still had more error as you were not selecting order_id on your intermediate table i2 so edited here as :
SELECT o1.order_id, o1.country, i2.brand,
SUM(o1.total_net_revenue)
FROM orders o1
INNER JOIN (
SELECT i1.brand, SUM(i1.net_revenue) AS total_net_revenue,order_id
FROM ordered_items i1
WHERE i1.country = 'France'
GROUP BY i1.brand
) i2
ON o1.order_id = i2.order_id AND o1.total_net_revenue = i2.total_net_revenue
AND o1.total_net_revenue = i2.total_net_revenue
WHERE o1.country = 'France' AND o1.created_at BETWEEN '2016-12-01' AND '2016-12-31'
GROUP BY 1,2,3
ORDER BY 4
LIMIT 10`
--EDIT stack Fan is correct that the o2.total_net_revenue exists. My confusion was because the data structure duplicated three columns between the tables, including one that was being looked for.
There were a couple errors with your SQL statement:
1. You were referencing an invalid column in your outer-select-SUM function. I believe you're actually after i2.total_net_revenue.
The table structure is terrible, the "important" columns (country, revenue, order_id) are duplicated between the two tables. I would also expect the revenue columns to share the same name, if they always have the same values in them. In the example, there's no difference between i1.net_revenue and o1.total_net_revenue.
In your inner join, you didn't reference i1.order_id, which meant that your "on" clause couldn't execute correctly.
PROTIP:
When you run into an issue like this, take all the complicated bits out of your query and get the base query working correctly first. THEN add your functions.
PROTIP:
In your GROUP BY clause, reference the actual columns, NOT the column numbers. It makes your query more robust.
This is the query I ended up with:
SELECT o1.order_id, o1.country, i2.brand,
SUM(i2.total_net_revenue) AS total_rev
FROM orders o1
INNER JOIN (
SELECT i1.order_id, i1.brand, SUM(i1.net_revenue) AS total_net_revenue
FROM ordered_items i1
WHERE i1.country = 'France'
GROUP BY i1.brand
) i2
ON o1.order_id = i2.order_id AND o1.total_net_revenue = i2.total_net_revenue
AND o1.total_net_revenue = i2.total_net_revenue
WHERE o1.country = 'France' AND o1.created_at BETWEEN '2016-12-01' AND '2016-12-31'
GROUP BY o1.order_id, o1.country, i2.brand
ORDER BY total_rev
LIMIT 10

Count, Group By, Subquery, Left Join not working as expected

This is puzzling me and no amount of the Google is helping me, hoping someone can point me in the right direction.
Please note that I have omitted some fields from the tables that don't relate to the question just to simplify things.
contacts
contact_id
name
email
contact_uuids
uuid
contact_id
visitor_activity
uuid
event
contact_communications
comm_id
contact_id
employee_id
Query
SELECT
`c`.*,
(SELECT COUNT(`log_id`) FROM `contact_communications` `cc` WHERE `cc`.`contact_id` = `c`.`contact_id`) as `num_comms`,
(SELECT MAX(`date`) FROM `contact_communications` `cc` WHERE `cc`.`contact_id` = `c`.`contact_id`) as `latest_date`,
(SELECT MIN(`date`) FROM `contact_communications` `cc` WHERE `cc`.`contact_id` = `c`.`contact_id`) as `first_date`,
(SELECT COUNT(`vaid`) FROM `visitor_activity` `va` WHERE `va`.`uuid` = `cu`.`uuid`) as `num_act`
FROM `contacts` `c`
LEFT JOIN `contact_uuids` `cu` ON `c`.`contact_id` = `cu`.`contact_id`
GROUP BY `c`.`contact_id`
ORDER BY `c`.`name` ASC
Some contacts have multiple UUIDs (upwards of 20 or 30).
When I perform the query WITHOUT the GROUP BY statement, I get the results I expect - a row returned for each UUID that exists for that contact, with the correct "num_comms" and "num_act" numbers.
However when I add the GROUP BY statement, the "num_comms" is a lot smaller then expected and the "num_act" returns only the value from the first row without the GROUP BY statement.
I tried doing a "WHERE NOT IN" in the subquery, however that simply crashed the server as it was far too intense.
So - how do I get this to add up all the COUNT values from the LEFT JOIN and not just return the first value?
Also if anyone can help me optimize this that would be great.
Two problems:
GROUP BY c.contact_id does not include all the non-aggregate columns. This is a MySQL extension. What you get is random values for the rows other than contact_id
The JOIN adds confusion. Your only use for visitor_activity is the COUNT(*) one it. But that does not make sense since it is limited to one UUID, whereas the row is limited to one contact_id. Rethink the purpose of that.
Remove this line:
(SELECT COUNT(`vaid`) FROM `visitor_activity` `va` WHERE `va`.`uuid` = `cu`.`uuid`) as `num_act`
and the rest may work ok.
I will continue with the assumption that you want the COUNT of all rows in visitor_activity for all the uuids associated with the one contact_id.
See if this:
( SELECT COUNT(*)
FROM `contacts` c2
JOIN `visitor_activity` USING(uuid)
WHERE c2.contact_id = c.contact_id as `num_act` ) AS num_act
will work for the last subquery. At the same time, remove the JOIN:
LEFT JOIN `contact_uuids` `cu` ON `c`.`contact_id` = `cu`.`contact_id`
Now, back to the other problem (the non-standard usage of GROUP BY). Assuming that contact_id is the PRIMARY KEY, then simply remove the
GROUP BY `c`.`contact_id`

Creating a subquery in Access

I am attempting to create a subquery in Access but I am receiving an error stating that one record can be returned by this subquery. I am wanting to find the top 10 companies that have the most pets then I want to know the name of those pets. I have never created a subquery before so I am not sure where I am going wrong. Here is what I have:
SELECT TOP 10 dbo_tGovenrnmentRegulatoryAgency.GovernmentRegulatoryAgency
(SELECT dbo_tPet.Pet
FROM dbo_tPet)
FROM dbo_tPet INNER JOIN dbo_tGovenrnmentRegulatoryAgency ON
dbo_tPet.GovernmentRegulatoryAgencyID =
dbo_tGovenrnmentRegulatoryAgency.GovernmentRegulatoryAgencyID
GROUP BY dbo_tGovenrnmentRegulatoryAgency.GovernmentRegulatoryAgency
ORDER BY Count(dbo_tPet.PetID) DESC;
Consider this solution, requiring a subquery in the WHERE IN () clause:
SELECT t1.GovernmentRegulatoryAgency, dbo_tPet.Pet,
FROM dbo_tPet
INNER JOIN dbo_tGovenrnmentRegulatoryAgency t1 ON
dbo_tPet.GovernmentRegulatoryAgencyID = t1.GovernmentRegulatoryAgencyID
WHERE t1.GovernmentRegulatoryAgency IN
(SELECT TOP 10 t2.GovernmentRegulatoryAgency
FROM dbo_tPet
INNER JOIN dbo_tGovenrnmentRegulatoryAgency t2 ON
dbo_tPet.GovernmentRegulatoryAgencyID = t2.GovernmentRegulatoryAgencyID
GROUP BY t2.GovernmentRegulatoryAgency
ORDER BY Count(dbo_tPet.Pet) DESC);
Table aliases are not needed but I include them for demonstration.
This should hopefully do it:
SELECT a.GovernmentRegulatoryAgency, t.NumOfPets
FROM dbo_tGovenrnmentRegulatoryAgency a
INNER JOIN (
SELECT TOP 10 p.GovernmentRegulatoryAgencyID, COUNT(p.PetID) AS NumOfPets
FROM dbo_tPet p
GROUP BY p.GovernmentRegulatoryAgencyID
ORDER BY COUNT(p.PetID) DESC
) t
ON a.GovernmentRegulatoryAgencyID = t.GovernmentRegulatoryAgencyID
In a nutshell, first get the nested query sorted, identifying what the relevant agencies are, then inner join back to the agency table to get the detail of the agencies so picked.

Incorrect group by and order by merge

I have couple tables joined in MySQL - one has many others.
And try to select items from one, ordered by min values from another table.
Without grouping in seems to be like this:
Code:
select `catalog_products`.id
, `catalog_products`.alias
, `tmpKits`.`minPrice`
from `catalog_products`
left join `product_kits` on `product_kits`.`product_id` = `catalog_products`.`id`
left join (
SELECT MIN(new_price) AS minPrice, id FROM product_kits GROUP BY id
) AS tmpKits on `tmpKits`.`id` = `product_kits`.`id`
where `category_id` in ('62')
order by product_kits.new_price ASC
Result:
But when I add group by, I get this:
Code:
select `catalog_products`.id
, `catalog_products`.alias
, `tmpKits`.`minPrice`
from `catalog_products`
left join `product_kits` on `product_kits`.`product_id` = `catalog_products`.`id`
left join (
SELECT MIN(new_price) AS minPrice, id FROM product_kits GROUP BY id
) AS tmpKits on `tmpKits`.`id` = `product_kits`.`id`
where `category_id` in ('62')
group by `catalog_products`.`id`
order by product_kits.new_price ASC
Result:
And this is incorrect sorting!
Somehow when I group this results, I get id 280 before 281!
But I need to get:
281|1600.00
280|2340.00
So, grouping breaks existing ordering!
For one, when you apply the GROUP BY to only one column, there is no guarantee that the values in the other columns will be consistently correct. Unfortunately, MySQL allows this type of SELECT/GROUPing to happen other products don't. Two, the syntax of using an ORDER BY in a subquery while allowed in MySQL is not allowed in other database products including SQL Server. You should use a solution that will return the proper result each time it is executed.
So the query will be:
For one, when you apply the GROUP BY to only one column, there is no guarantee that the values in the other columns will be consistently correct. Unfortunately, MySQL allows this type of SELECT/GROUPing to happen other products don't. Two, the syntax of using an ORDER BY in a subquery while allowed in MySQL is not allowed in other database products including SQL Server. You should use a solution that will return the proper result each time it is executed.
So the query will be:
select CP.`id`, CP.`alias`, TK.`minPrice`
from catalog_products CP
left join `product_kits` PK on PK.`product_id` = CP.`id`
left join (
SELECT MIN(`new_price`) AS "minPrice", `id` FROM product_kits GROUP BY `id`
) AS TK on TK.`id` = PK.`id`
where CP.`category_id` IN ('62')
order by PK.`new_price` ASC
group by CP.`id`
The thing is that group by does not recognize order by in MySQL.
Actually, what I was doing is really bad practice.
In this case you should use distinct and by catalog_products.*
In my opinion, group by is really useful when you need group result of agregated functions.
Otherwise you should not use it to get unique values.

MySql query runs very slow(actually never gives output) without where clause

I have a mysql query and it works fine when i use where clause, but when i donot use
where clause it gone and never gives the output and finally timeout.
Actually i have used Explain command to check the performance of the query and in both cases the Explain gives the same number of rows used in joining.
I have attached the image of output got with Explain command.
Below is the query.
I couldn't figure whats the problem here.
Any help is highly appreciated.
Thanks.
SELECT
MCI.CLIENT_ID AS CLIENT_ID, MCI.NAME AS CLIENT_NAME, MCI.PRIMARY_CONTACT AS CLIENT_PRIMARY_CONTACT,
MCI.ADDED_BY AS SP_ID, CONCAT(MUD_SP.FIRST_NAME, ' ', MUD_SP.LAST_NAME) AS SP_NAME,
MCI.FK_PROSPECT_ID AS PROSPECT_ID, MCI.DATE_ADDED AS ADDED_ON,
(SELECT GROUP_CONCAT(LT.TAG_TEXT SEPARATOR ', ')
FROM LK_TAG LT
INNER JOIN M_OBJECT_TAG_MAPPING MOTM
ON LT.PK_ID = MOTM.FK_TAG_ID
WHERE MOTM.FK_OBJECT_ID = MCI.FK_PROSPECT_ID
AND MOTM.OBJECT_TYPE = 1
AND MOTM.IS_ACTIVE = 1
) AS TAGS,
IFNULL(SUM(GET_DIGITS(MMR.RCP_AMOUNT)), 0) AS REVENUE_SO_FAR,
IFNULL(SUM(GET_DIGITS(MMR.RCP_RUPEES)), 0) AS REVENUE_INR,
COUNT(DISTINCT PMI_MONTHLY.PROJECT_ID) AS MONTHLY,
COUNT(DISTINCT PMI_FIXED.PROJECT_ID) AS FIXED,
COUNT(DISTINCT PMI_HOURLY.PROJECT_ID) AS HOURLY,
COUNT(DISTINCT PMI_ANNUAL.PROJECT_ID) AS ANNUAL,
COUNT(DISTINCT PMI_CURRENTLY_RUNNING.PROJECT_ID) AS CURRENTLY_RUNNING_PROJECTS,
COUNT(DISTINCT PMI_YET_TO_START.PROJECT_ID) AS YET_TO_START_PROJECTS,
COUNT(DISTINCT PMI_TECH_SALES_CLOSED.PROJECT_ID) AS TECH_SALES_CLOSED_PROJECTS
FROM
M_CLIENT_INFO MCI
INNER JOIN M_USER_DETAILS MUD_SP
ON MCI.ADDED_BY = MUD_SP.PK_ID
LEFT OUTER JOIN M_MONTH_RECEIPT MMR
ON MMR.CLIENT_ID = MCI.CLIENT_ID
LEFT OUTER JOIN M_PROJECT_INFO PMI_FIXED
ON PMI_FIXED.CLIENT_ID = MCI.CLIENT_ID AND PMI_FIXED.PROJECT_TYPE = 1
LEFT OUTER JOIN M_PROJECT_INFO PMI_MONTHLY
ON PMI_MONTHLY.CLIENT_ID = MCI.CLIENT_ID AND PMI_MONTHLY.PROJECT_TYPE = 2
LEFT OUTER JOIN M_PROJECT_INFO PMI_HOURLY
ON PMI_HOURLY.CLIENT_ID = MCI.CLIENT_ID AND PMI_HOURLY.PROJECT_TYPE = 3
LEFT OUTER JOIN M_PROJECT_INFO PMI_ANNUAL
ON PMI_ANNUAL.CLIENT_ID = MCI.CLIENT_ID AND PMI_ANNUAL.PROJECT_TYPE = 4
LEFT OUTER JOIN M_PROJECT_INFO PMI_CURRENTLY_RUNNING
ON PMI_CURRENTLY_RUNNING.CLIENT_ID = MCI.CLIENT_ID AND PMI_CURRENTLY_RUNNING.STATUS = 4
LEFT OUTER JOIN M_PROJECT_INFO PMI_YET_TO_START
ON PMI_YET_TO_START.CLIENT_ID = MCI.CLIENT_ID AND PMI_YET_TO_START.STATUS < 4
LEFT OUTER JOIN M_PROJECT_INFO PMI_TECH_SALES_CLOSED
ON PMI_TECH_SALES_CLOSED.CLIENT_ID = MCI.CLIENT_ID AND PMI_TECH_SALES_CLOSED.STATUS > 4
WHERE YEAR(MCI.DATE_ADDED) = '2012'
GROUP BY MCI.CLIENT_ID ORDER BY CLIENT_NAME ASC
Yes, as many people have said, the key is that when you have the where clause, mysql engine filters the table M_CLIENT_INFO --probably drammatically--.
A similar result as removing the where clause is to to add this where clause:
where 1 = 1
You will see that the performance is degraded also because mysql will try to get all the data.
Remove the where clause and all columns from select and add a count to see how many records you get. If it is reasonable, say up to 10k, then do the following,
put back the select columns related to M_CLIENT_INFO
do not include the nested one "TAGS"
remove all your joins
run your query without where clause and gradually include the joins
this way you'll find out when the timeout is caused.
I would try the following. First, MySQL has a keyword "STRAIGHT_JOIN" which tells the optimizer to do the query in the table order you've specified. Since all you left-joins are child-related (like a lookup table), you don't want MySQL to try and interpret one of those as a primary basis of the query.
SELECT STRAIGHT_JOIN ... rest of query.
Next, your M_PROJECT_INFO table, I dont know how many columns of data are out there, but you appear to be concentrating on just a few columns on your DISTINCT aggregates. I would make sure you have a covering index on these elements to help the query via an index on
( Client_ID, Project_Type, Status, Project_ID )
This way the engine can apply the criteria and get the distinct all out of the index instead of having to go back to the raw data pages for the query.
Third, your M_CLIENT_INFO table. Ensure that has an index on both your criteria, group by AND your Order By, and change your order by from the aliased "CLIENT_NAME" to the actual column of the SQL table so it matches the index
( Date_Added, Client_ID, Name )
I have "name" in ticks as it is also a reserved word and helps clarify the column, not the keyword.
Next, the WHERE clause. Whenever you apply a function to an indexed column name, it doesn't work the greatest, especially on date/time fields... You might want to change your where clause to
WHERE MCI.Date_Added between '2012-01-01' and '2012-12-31 23:59:59'
so the BETWEEN range is showing the entire year and the index can better be utilized.
Finally, if the above do not help, I would consider splitting your query some. The GROUP_CONCACT inline select for the TAGS might be a bit of a killer for you. You might want to have all the distinct elements first for the grouping per client, THEN get those details.... Something like
select
PQ.*,
group_concat(...) tags
from
( the entire primary part of the query ) as PQ
Left join yourGroupConcatTableBasis on key columns