In MySQL, I have a two tables as below :
ClientTable
clientID clientName
1 Client A
2 Client B
3 Client C
4 Client D
5 Client E
6 Client F
NotesTable
noteID clientID note noteDate
1 3 Test 1 12-Jun-14
2 3 Test 2 18-Aug-14
3 4 Test 3 23-Oct-14
4 6 Test 4 25-May-14
5 3 Test 5 25-Nov-14
6 6 Test 6 16-Jul-14
I want to select all the clients from the client table and, where a note exists for the client, the date of the latest note entry. If no note exists for a client, then return null for the noteDate. Desired result set as follows :
client ID clientName latestNoteDate
1 Client A null
2 Client B null
3 Client C 25-Nov-14
4 Client D 23-Oct-14
5 Client E null
6 Client F 16-Jul-14
Any help appreciated, I have tried a few options using nested Select with MAX(noteDate) and various left joins but can't seem to get it right.
Why all the subqueries?
select ct.clientID, ct.clientName,max(nt.noteDate) latestNoteDate
from ClientTable ct
left outer join NotesTable nt
on ct.clientID = nt.clientID
group by ct.clientID, ct.clientName
You can use an outer join with a subquery:
select c.clientid, c.clientname, n.latestnotedate
from client c
left join (
select clientId, max(noteDate) latestnotedate
from notes
group by clientId
) n on c.clientId = n.clientId
This assumes the max(noteDate) is the latest note entry. If that's not the case, easy enough to use the noteid instead and then just include one additional join.
Looks like a good place for using a sub-query. Try something like:
select c.id, c.name, n.latestNoteDate from client c
left join
(select clientid, MAX(notedate) as latestNoteDate from note
group by clientid) as n on n.clientid = c.id
The key is, find the data you want from the notes table first, then use that to join with the client data later.
Try the following code, which uses a correlated sub-query.
SELECT ct.clientID,
ct.clientName,
(SELECT MAX(noteDate)
FROM notesTable nt
WHERE nt.clientID = ct.clientId)
FROM clientTable ct
select clienttable.clientID, clienttable.clientName, notes.noteDate
left outer join NotesTable notes on notes.clientID = clienttable.clientID and noteDate = (select max(noteDate) from NotesTable where notes.clientID = clienttable.clientID)
It will return null if there are no note entries.
OR
select clienttable, clientID, clienttable.clientName, (select max(noteDate) from NotesTable where notes.clientID = clienttable.clientID) noteDate
Related
see the EARD scenario
Major_applied_for table
id
preference
application_number (fk)
major_code (fk)
1
1
2
1
2
1
1
1
3
3
3
1
4
2
1
2
5
2
2
2
Some Clarifications:
• The code attribute of Major table holds (1)CS for computer science, (2)BMS for business management and so on.
• preference attribute of Major_Applied_For is 1, 2 or 3 (1 for being the first
choice, 2 being the second choice and 3 being the third choice)
.
.
.
This is a table that many to many relationship resolved in, I wanna get all the application numbers that have CS as the first choice and BMS as the second choice.
I tried this sql statement but it's logically incorrect.
SELECT m.id, CONCAT(m.fname, " ", m.lname) AS Fullname, app.number AS application_no
FROM applicant m, application app, major_applied_for mjaf
WHERE ((mjaf.major_code = 1 AND mjaf.preference = 1) AND (mjaf.major_code = 2 AND mjaf.preference = 2) AND (mjaf.application_number = app.number AND app.applicant_id = m.id));
How can I resolve this issue?
Find the applicants with CS as their first pref, find the applicants with BMS their second pref. Inner join these two sets and check their names.
with first_cs as (
select c.applicant_id
from major_applied_for a inner join major b on a.major_code = b.code and a.preference = 1 and b.name = 'CS'
inner join application c on a.application_number = c.number ), second_bms as(
select c.applicant_id
from major_applied_for a inner join major b on a.major_code = b.code and a.preference = 2 and b.name = 'BMS'
inner join application c on a.application_number = c.number ) select fname,
lname from first_cs a inner join second_bms b on a.applicant_id = b.applicant_id
inner join applicant c on a.applicant_id = c.id
I have a strange result when performing a lateral join on a query
I have the following table structure
task->id
comment -> id , taskId, comment
tasklink -> taskId, type, userid
with a single task record (id 10), 1 comment record ("row1", "a test comment") and 5 tasklink records (all with taskid 10)
I expected this query
select task.id,
json_agg(json_build_object('id',c.id, 'user',c.comment)) as comments,
json_agg(json_build_object('type',b.type, 'user',b.userid)) as users
FROM task
left join lateral (select c.* from comment c where task.id = c.taskid) c on true
left join lateral (select b.* from taskuserlink b where task.id = b.taskid) b on true
where task.id = 10
GROUP BY task.id ;
to return
id | comments | users
---------------------------------------------------------------------
10 "[{"id":"row1","user":"a test comment"}]" "[{"type":"updatedBy","user":1},"type":"closedBy","user":5},"type":"updatedBy","user":5},"type":"createdBy","user":5},{"type":"ownedBy","user":5}]"
instead, I got this
id | comments | users
10 "[{"id":"row1","user":"a test comment"},{"id":"row1","user":"a test comment"},{"id":"row1","user":"a test comment"},{"id":"row1","user":"a test comment"},{"id":"row1","user":"a test comment"}]" "[{"type":"updatedBy","user":1},{"type":"closedBy","user":5},{"type":"updatedBy","user":5},{"type":"createdBy","user":5},{"type":"ownedBy","user":5}]"
ie , for every link row, the comment row is duplicated
I am thinking that I am missing something really obvious, but as I have only just started using Postgres (and sql ) I'm a little stumped
I would appreciate some guidance on where I'm going wrong
Move the aggregates into subqueries:
select id, comments, users
from task t
left join lateral (
select json_agg(json_build_object('id',c.id, 'user',c.comment)) as comments
from comment c
where t.id = c.taskid
) c on true
left join lateral (
select json_agg(json_build_object('type',b.type, 'user',b.userid)) as users
from taskuserlink b
where t.id = b.taskid
) b on true
DbFiddle.
So guys, trying to write a query to get the count of statuses where project_id = ? and statuses in 'New' from a couple of tables so let me break it down.
I have these three tables
Case_Status
id case_status
1 New
2 Failed
3. Accepted
Referral
id case_status_id project_id application_id
1 1 1 20
2 2 1 21
Project
id name
1 project1
2 project2
So this is my query
SELECT COUNT(referrals.id) AS count_all, case_statuses.case_status AS counted
FROM "case_statuses" LEFT OUTER JOIN "referrals" ON "referrals"."case_status_id" = "case_statuses"."id"
WHERE "case_statuses"."deleted_at" IS NULL AND (case_statuses.case_status IN ('New') AND referrals.project_id = 1)
GROUP BY case_statuses.case_status;
This is my result
count_all counted
1 New
1 Failed
But I am expecting this result instead
count_all counted
1 New
1 Failed
0 Accepted
Does anyone know what's wrong with my query that isnt showing count for all the case_statuses?
Thanks
Conditions on the second table (in a left join) should be in the on clause:
SELECT COUNT(r.id) AS count_all, cs.case_status AS counted
FROM case_statuses cs LEFT OUTER JOIN
referrals r
ON r.case_status_id = cs.id AND r.project_id = 1
WHERE cs.deleted_at IS NULL AND cs.case_status NOT IN ('New')
GROUP BY cs.case_status;
Otherwise, the WHERE clause turns the outer join into an inner join.
change your query like this
SELECT COUNT(referrals.id) AS count_all, case_statuses.case_status AS counted
FROM "case_statuses" LEFT JOIN "referrals" ON "referrals"."case_status_id" = "case_statuses"."id" AND referrals.project_id = 1
WHERE "case_statuses"."deleted_at" IS NULL AND case_statuses.case_status NOT IN ('New')
GROUP BY case_statuses.case_status;
Given your data and the expected result you just need to loose the WHERE clause.
SELECT COUNT(referrals.id) AS count_all, case_statuses.case_status AS counted
FROM case_statuses
LEFT OUTER JOIN referrals ON referrals.case_status_id = case_statuses.id
GROUP BY case_statuses.case_status;
See this fiddle for details.
(The example that follows is hypothetical, but illustrates the concept).
Using MySQL, say I have 2 tables:
userFromID userToId moreInfo
1 2 cat
1 3 dog
4 1 bear
3 4 fish
And...
userId someInfo addlInfo
1 m 32
2 f 33
3 m 25
4 f 28
And I want to query for a user id, and get back joined info from both tables for all users that share a relationship with user1.
assume that the first table has something like alter table thatFirstTable add unique index(userFromId, userToId) so there won't be any duplicates - each relationship between the two ids will be unique.
it doesn't matter who's the "from" or "to"
so the desired result would be something like this, if queried for relationships with user id: 1
userId moreInfo someInfo addlInfo
2 cat f 33
3 dog m 25
4 bear f 28
Thanks.
/EDIT this "works" but I suspect there's a better way?
SELECT * FROM users JOIN friends ON friends.userFrom = users.id OR friends.userTo = users.id WHERE users.id != 1 AND friends.userFrom = 1 OR friends.userTo = 1
/EDIT2 - I updated the sample output to better reflect the goal
try this query::
select tbl2.userid,tbl1.moreinfo,
tbl2.someinfo,tbl2.addinfo
from tbl1 join tbl2
on (tbl1.usertoid = tbl2.userid and tbl1.userfromid = 1)
You should just join the tables with the query below.
select u.userId, f.moreInfo, u.someInfo, u.addlInfo
from users AS u INNER JOIN friends AS f ON u.userId = f.UserToId
where f.userFrom = 1
Try this. Tested and 100% working
select a.userToID, a.moreInfo, b.someInfo, b.addInfo from tbl1 a
left outer join
tbl2 b on a.userToID = b.userId
where a.userFromID = 1;
i have a details table with columns:
user_id int
code int
value int
And i want to build a summary table that looks like:
user_id int
valueA int
valueB int
In the details table, valueA would correspond to say, code 5, and valueB would correspond to say, code 6, so i'm looking for something like:
insert into summary (user_id,valueA,valueB) VALUES ( SELECT ??? from details );
The problem of course is that i'm looking at multiple rows from the "details" table to populate one row in the "summary" table.
Eg, if i had the following rows in details:
1 5 100
1 6 200
2 5 1000
2 6 2000
I want to end up with the following in the summary table:
1 100 200
2 1000 2000
Any ideas?
MySQL doesn't have PIVOT/UNPIVOT syntax, which leaves you to use a combination of GROUP BY and CASE expressions:
INSERT INTO SUMMARY
(user_id,valueA,valueB)
SELECT d.user_id,
MAX(CASE WHEN d.code = 5 THEN d.value ELSE NULL END),
MAX(CASE WHEN d.code = 6 THEN d.value ELSE NULL END),
FROM DETAILS d
GROUP BY d.user_id
insert into summary (user_id,valueA,valueB)
SELECT a.user_id, a.value, b.value
from details a
join details b on a.user_id = b.user_id
WHERE a.code = 5 and b.code = 6;
beware: you will end up with multiple summary columns if user_id+code is not unique.
EDIT:
insert into summary (user_id,valueA,valueB)
select u.user_id, ifnull(a.value,0), ifnull(b.value,0)
from (select distinct user_id from details /* where code in (5,6) */) u
left join details a on a.user_id = u.user_id and a.code = 5
left join details b on b.user_id = u.user_id and b.code = 6
If you have a manageable set of codes (say just 5 and 6) you could do something like this:
SELECT details.user_id, code5.value, code6.value
FROM details JOIN
(SELECT user_id, value FROM details WHERE code = 5) AS code5 USING(user_id)
JOIN
(SELECT user_id, value FROM details WHERE code = 6) AS code6 USING(user_id);
You may need to modify your JOINs depending on if your codes are not required as 1 to 1 relationship (i.e. LEFT JOINs).
If you have a large set of codes, I would look into a cursor runs a similar query above over a result set of your codes or using a different technology, (i.e. PHP script).