I'm joining plenty of tables together, I want to count the number city of a company in the company2city table, and at same time link that to a row in the company table and then find out if the endtime is more than now.. The company2city is a many to many table that is linked together with the city table. A company can have many cities, and it is in the company2city table.
SELECT COUNT(company2city.cityid) as location, city.city
FROM company
INNER JOIN company2city ON company.id = company2city.companyid
INNER JOIN city ON company2city.cityid = city.id AND company.endtime > now()
GROUP BY company2city.cityid
That select statement works, but it only select those cities that have an instance in the company2city table and if the company.endtime is more than now(). What I want is to select also all the cities in the city table, and if the company.endtime() > now() failed it will just make the COUNT(company2city.cityid) as location = 0
How can I do such select statement?
I believe that what you want is a Left Join instead of an Inner Join. A left join joins regardless and returns null where it could not make a join.
Try this
SELECT COUNT(company2city.cityid) as location, city.city
FROM city
LEFT JOIN company2city on city.id = company2city.cityid
LEFT JOIN company on company.id = company2city.companyid
where company.endtime > now()
group by city.city
I think something along the lines of
SELECT COALESCE (COUNT (company2city.cityid), NULL) AS location, city.city
FROM company
LEFT JOIN company2city
ON company.id = company2city.companyid
LEFT JOIN city
ON company2city.cityid = city.id AND company.endtime > now ()
GROUP BY company2city.cityid
should work for you. I've never actually tried the coalece in the select with MYSQL but I know it will work with Oracle. But the key is using Left joins instead of the inner joins.
Related
Iam currently trying to left join a table on a left joined table as follows.
I have the tables:
accounts (id, vorname, nachname)
projektkurse (id, accounts_id, projektwochen_id)
projektkurs_einzel (id, projektkurse_id)
projektkurs_einzel_zeiten (id, date, shift, projektkurs_einzel_id)
Now I want to get every account and the amount times they have an entry inside of projektkurs_einzel_zeiten, which should also be unique. So having the same date and shift multiple times does not count as multiple entries. The result should also be limited by the column projektwochen_id from the table projektkurse. This column should match a certain value for example 8.
Some Accounts don't have any entries in projektkurse, projektkurs_einzel and projektkurs_einzel_zeiten, this is why my first thought was using LEFT JOIN like this:
SELECT accounts.id, accounts.vorname, accounts.nachname, COUNT(DISTINCT projektkurs_einzel_zeiten.date, projektkurs_einzel_zeiten.shift) AS T
FROM accounts
LEFT JOIN projektkurse on accounts.id = projektkurse.creator_id
LEFT JOIN projektkurs_einzel on projektkurse.id = projektkurs_einzel.projektkurs_id
LEFT JOIN projektkurs_einzel_zeiten ON projektkurs_einzel.id = projektkurs_einzel_zeiten.projektkurs_einzel_id
WHERE projektkurse.projektwochen_id = 8
GROUP BY accounts.id
This query does not achieve exactly what I want. It only returns accounts that have atleast one entry in projektkurse even if they have none in projektkurs_einzel and projektkurs_einzel_zeiten. The Count is obviously 0 for them but the accounts that have no entries in projektkurse are being ignored completly.
How can I also show the accounts that don't have entries in any other table with the Count 0 aswell?
I would recommend writing the query like this:
SELECT a.id, a.vorname, a.nachname,
COUNT(DISTINCT pez.date, pez.shift) AS T
FROM accounts a LEFT JOIN
projektkurse
ON a.id = pk.creator_id AND
pk.projektwochen_id = 8 LEFT JOIN
projektkurs_einzel pe
ON pk.id = pe.projektkurs_id LEFT JOIN
projektkurs_einzel_zeiten pez
ON pe.id = pez.projektkurs_einzel_id
GROUP BY a.id, a.vorname, a.nachname;
Notes:
Your problem is fixed by moving the WHERE condition to the ON clause. Your WHERE turns the outer join into an inner join, because NULL values do not match.
Table aliases make the query easier to write and to read.
It is a best practice to include all unaggregated columns in the GROUP BY. However, assuming that id is unique, your formulation is okay (due to something called "functional dependencies").
You should not use eft join table's column ins where condition this work as inner join
You should move the where condition for a left joined table in the corresponding ON clause
SELECT accounts.id, accounts.vorname, accounts.nachname, COUNT(DISTINCT projektkurs_einzel_zeiten.date, projektkurs_einzel_zeiten.shift) AS T
FROM accounts
LEFT JOIN projektkurse on accounts.id = projektkurse.creator_id
AND projektkurse.projektwochen_id = 8
LEFT JOIN projektkurs_einzel on projektkurse.id = projektkurs_einzel.projektkurs_id
LEFT JOIN projektkurs_einzel_zeiten ON projektkurs_einzel.id = projektkurs_einzel_zeiten.projektkurs_einzel_id
GROUP BY accounts.id
I have two tables:
reviewStatusPhases - id|name
and
userPhase - id|reviewStatusPhase_id|user_id|created_at|updated_at
The reviewStatusPhases table have records inserted (Active, Inactive, On Pause, Terminated...), and userPhase is empty.
The tables are connected via
userPhase.reviewStatusPhase_id = reviewStatusPhases.id
one to one.
Is it possible that in one query I get all reviewStatusPhases, and cound how many users are in each phase? In this case I will get something like this:
Active (0 Users)
Inactive (0 Users)
On Pause (0 Users)
Terminated (0 Users)
I'm making some assumptions here (e.g. INNER JOIN versus LEFT JOIN in the join, and DISTINCT in the count), but it sounds like you just want
SELECT reviewStatusPhases.name, COUNT(DISTINCT userPhase.user_id)
FROM userPhase INNER JOIN reviewStatusPhases
ON userPhase.reviewStatusPhase_id = reviewStatusPhases.id
GROUP BY reviewStatusPhases.name
Query will be as follows:
SELECT r.name as `name`, count(u.id) as `count` FROM reviewStatusPhases r LEFT OUTER JOIN userPhase u ON r.id = u.reviewStatusPhase_id GROUP BY r.name
left outer join with reviewStatusPhases on left to show all names.
group by names of reviewStatusPhases.
display reviewStatusPhases name and count of user id's (to neglect null values)
Use LEFT JOIN as follows:
SELECT COUNT(m.UserId) FROM Table1 m
LEFT JOIN Table2 k ON k.StatusId = m.StatusId
WHERE k.Status = 'Inactive'
You can easily use the Status column to track the users and their activities. In your case, ReviewStatus.
I hope the following will be helpful
SELECT RPS.Name, COUNT(UP.user_id)
FROM reviewStatusPhases RPS
LEFT OUTER JOIN userphases UP ON RPS.id = UP.reviewStatusPhase_id
GROUP BY RPS.Name
ORDER BY RPS.Name
SELECT
DISTINCT s.s_level AS 'Level',
COUNT(DISTINCT s.s_id) AS Schools,
COUNT(DISTINCT st.st_id) AS Teachers
FROM schools AS s
JOIN school_teachers AS st ON st.st_school_idFk = s.s_id AND st.st_status = 1
WHERE s.s_status = 1
GROUP BY s.s_level
I want to write a query that can show the amount of purchases made in the month of June, grouped by city. So I wrote this query:
SELECT state, city, COUNT(*)
FROM address
JOIN person
JOIN purchase
WHERE purchase.person_FK = person.id
AND address.person_FK = person.id
AND MONTH(purchase.purchase_date) = 5
GROUP BY state, city
ORDER BY state, city;
But this query doesn't return the cities that have no purchases in that month, and I want to show them. Can you help me?
You need a city table with all the cities, then do a LEFT JOIN.
And put the JOIN condition on the ON section not the WHERE
SELECT Cities.state, Cities.city, COUNT(*)
FROM Cities
LEFT JOIN Purchase
ON Cities.city = Purchase.city
AND Cities.state = Cities.state
JOIN person
ON purchase.person_FK = person.id
AND MONTH(purchase.purchase_date) = 5
JOIN address
ON address.person_FK = person.id
GROUP BY Cities.state, Cities.city
ORDER BY Citiesstate, Cities.city;
Look at your joins, 'JOIN' is the same as 'INNER JOIN' which only shows results which is in both tables, you'll need to use a LEFT or FULL join to get what you need.
Theres a diagram here which explains them well
You will need to have a table that provides a listing of all cities you want to show (if you don't already have that). Then you join to the city table as well. Otherwise, your query has no idea which cities to show with a zero count. In addition, you will need to change your JOIN's to LEFT JOIN's
SELECT city.state, city.city, COUNT(*)
FROM address
LEFT JOIN person ON person.id = address.person_FK
LEFT JOIN purchase ON purchase.person_FK = person.id
LEFT JOIN city ON purchase.city = city.city
WHERE MONTH(purchase.purchase_date) = 5
GROUP BY address.state, address.city
ORDER BY address.state, address.city;
I'm using 4 tables
CUSTOMER
CUSTOMER_ORDER
CUST_ORDER_LINE
CUST_ADDRESS
I used Inner joins to link the tables. CUSTOMER is linked to CUSTOMER_ORDER and CUST_ADDRESS by customer_ID, and CUSTOMER_ORDER_LINE is linked to CUSTOMER_ORDER by order_ID. Order_ID does not appear in the CUSTOMER or CUST_ADDRESS tables.
When I run the query below, I get every shipping address on record for that particular customer and order number.
For example, a distributor has 25 possible shipping addresses, but they only ship one order to one shipping address at a time. My query is bringing back one order number 25 times for every address. Any advice would be wonderful. Thank you.
SELECT DISTINCT TOP (100) PERCENT dbo.CUSTOMER_ORDER.ID,
dbo.CUSTOMER.NAME,
dbo.CUST_ORDER_LINE.PART_ID,
dbo.CUST_ORDER_LINE.ORDER_QTY,
dbo.CUSTOMER_ORDER.STATUS,
dbo.CUSTOMER_ORDER.SHIPTO_ID,
dbo.CUST_ADDRESS.NAME AS Expr1
FROM dbo.CUSTOMER
INNER JOIN dbo.CUSTOMER_ORDER
ON dbo.CUSTOMER.ID = dbo.CUSTOMER_ORDER.CUSTOMER_ID
INNER JOIN dbo.CUST_ORDER_LINE
ON dbo.CUSTOMER_ORDER.ID = dbo.CUST_ORDER_LINE.CUST_ORDER_ID
INNER JOIN dbo.CUST_ADDRESS
ON dbo.CUSTOMER.ID = dbo.CUST_ADDRESS.CUSTOMER_ID
WHERE (dbo.CUSTOMER_ORDER.ORDER_DATE > '1/1/2014')
AND (dbo.CUSTOMER_ORDER.ID NOT LIKE 'RMA%')
GROUP BY dbo.CUSTOMER_ORDER.ID,
dbo.CUSTOMER.NAME,
dbo.CUST_ORDER_LINE.PART_ID,
dbo.CUST_ORDER_LINE.ORDER_QTY,
dbo.CUSTOMER_ORDER.STATUS,
dbo.CUSTOMER_ORDER.SHIPTO_ID,
dbo.CUST_ADDRESS.NAME
ORDER BY dbo.CUSTOMER_ORDER.ID
As a shot in the dark it seems your query should be something like this.
SELECT
co.ID,
c.NAME,
col.PART_ID,
col.ORDER_QTY,
co.STATUS,
co.SHIPTO_ID,
ca.NAME AS Expr1
FROM dbo.CUSTOMER c
INNER JOIN dbo.CUSTOMER_ORDER co ON c.ID = co.CUSTOMER_ID
INNER JOIN dbo.CUST_ORDER_LINE col ON co.ID = col.CUST_ORDER_ID
INNER JOIN dbo.CUST_ADDRESS ca ON co.SHIPTO_ID = ca.CUSTOMER_ID --this is now joining to the order table.
WHERE co.ORDER_DATE > '2014-01-01'
AND co.ID NOT LIKE 'RMA%'
GROUP BY co.ID,
c.NAME,
col.PART_ID,
col.ORDER_QTY,
co.STATUS,
co.SHIPTO_ID,
ca.NAME
ORDER BY co.ID
Notice how using aliases makes this look a lot cleaner. I also changed up the string date to use the generally accepted format. This will work regardless of your DATEFORMAT setting.
i have a MySQL SELECT query which fetches data from 6 tables using Mysql JOIN. here is the MySQL query i am using.
SELECT
u.id,u.password,
u.registerDate,
u.lastVisitDate,
u.lastVisitIp,
u.activationString,
u.active,
u.block,
u.gender,
u.contact_id,
c.name,
c.email,
c.pPhone,
c.sPhone,
c.area_id,
a.name as areaName,
a.city_id,
ct.name as cityName,
ct.state_id,
s.name as stateName,
s.country_id,
cn.name as countryName
FROM users u
LEFT JOIN contacts c ON (u.contact_id = c.id)
LEFT JOIN areas a ON (c.area_id = a.id)
LEFT JOIN cities ct ON (a.city_id = ct.id)
LEFT JOIN states s ON (ct.state_id = s.id)
LEFT JOIN countries cn ON (s.country_id = c.id)
although query works perfectly fine it sometimes returns duplicate results if it finds any duplicate values when using LEFT JOIN. for example in contacts table there exist two rows with area id '2' which results in returning another duplicated row. how do i make a query to select only the required result without any duplicate row. is there any different type of MySQL Join i should be using?
thank you
UPDATE :
here is the contacts table, the column area_id may have several duplicate values.
ANSWER :
there was an error in my condition in last LEFT JOIN where i have used (s.country_id = c.id) instead it should be (s.country_id = cn.id) after splitting the query and testing individually i got to track the error. thank you for your response. it works perfectly fine now.
Duplicating the rows like you mentioned seems to indicate a data problem.
If users is your most granular table this shouldn't happen.
I'd guess, then, that it's possible for a single user to have multiple entries in contacts
You could use DISTINCT as mentioned by #dxprog but I think that GROUP BY is more appropriate here. GROUP BY whichever datapoint could potentially be duplicated....
After all, if a user has corresponding contact records, which one are you intending to JOIN to?
You must specify this if you want to remove "duplicates" because, as far as the RDBMS is concerned, the two rows matching
LEFT JOIN contacts c ON (u.contact_id = c.id)
Are, in fact, distinct already
I think a DISTINCT may be what you're looking for:
SELECT DISTINCT
u.id,u.password,
u.registerDate,
u.lastVisitDate,
u.lastVisitIp,
u.activationString,
u.active,
u.block,
u.gender,
u.contact_id,
c.name,
c.email,
c.pPhone,
c.sPhone,
c.area_id,
a.name as areaName,
a.city_id,
ct.name as cityName,
ct.state_id,
s.name as stateName,
s.country_id,
cn.name as countryName
FROM users u
LEFT JOIN contacts c ON (u.contact_id = c.id)
LEFT JOIN areas a ON (c.area_id = a.id)
LEFT JOIN cities ct ON (a.city_id = ct.id)
LEFT JOIN states s ON (ct.state_id = s.id)
LEFT JOIN countries cn ON (s.country_id = c.id)
This should only return rows where the user ID is distinct, though you may not get all the joined data you'd hoped for.