I need to present a flag - 0 if a condition is not meet, 1 if it is - and I can do it in two different ways :
Get Employee ID, name, 1 if has others in suborder - 0 if not :
SELECT e.ID
, e.Name
, ISNULL ( ( SELECT TOP 1 1 FROM Employee se WHERE se.ManagerID = e.ID ) , 0 ) AS HasSubordinates
FROM Employee e
or
SELECT e.ID
, e.Name
, ISNULL ( ( SELECT 1 WHERE EXISTS ( SELECT * FROM Employee se WHERE se.ManagerID = e.ID ) ) , 0 ) AS HasSubordinates
FROM Employee e
Which version would you choose and why ?
Update 1
How about this one ?
SELECT o.ID
, o.Name
, o.StartDate
, o.EndDate
, ISNULL ( ( SELECT TOP 1 1 FROM changes c WHERE c.ChangeDate BETWEEN o.StartDate AND o.EndDate ) , 0 ) AS IsChanged
FROM Orders o
or
SELECT o.ID
, o.Name
, o.StartDate
, o.EndDate
, ISNULL ( ( SELECT 1 WHERE EXISTS ( SELECT * FROM changes c WHERE c.ChangeDate BETWEEN o.StartDate AND o.EndDate ) ), 0 ) AS IsChanged
FROM Orders o
Neither, I'd use:
SELECT t.id,
t.name,
CASE WHEN x.managerid IS NULL THEN 0 ELSE 1 END AS HasSubordinates
FROM EMPLOYEE t
LEFT JOIN (SELECT DISTINCT
e.managerid
FROM EMPLOYEE e) x ON x.managerid = t.id
...because correlated SELECTS in the SELECT clause are bad - they do not scale, because they execute for every row returned. Which means the more rows you have, the more times the correlated SELECT will be called.
I wouldn't do either...
The reason being that (and this is as far as I know) when you have a subselect in the select statement, that subselect will be executed once for every row that is returned. Hence if you had 100 rows returned by the main query you would in effect be running 101 queries. When you use a join you are only doing one query that needs to match the left and the right together. Note it would help if you have an index on ManagerId.
Try something like this:
SELECT e.ID,
e.Name,
COUNT(se.ID) AS TotalStaff
FROM Employee e
LEFT JOIN Employee se
ON se.ManagerID = e.ID
GROUP BY e.ID, e.Name
This is slightly different to what you had as I am returning the total and not just a 0|1 but that is easy to change if you need the 1|0...
Let me know if this helps
Related
select C.Id as candidateId,C.Name, C.Phone, Status.ResultStatusText , Status.TimeStamp, Status.notes ,
(Select count(*) from CandidateCallHistory where CandiateId = candidateId) AS numbCalls,
(SELECT SUBSTRING((SELECT ',' + Name
FROM Jobs
WHERE Id in (select value from fn_Split(c.JobIds,','))
FOR XML PATH('')),2,200000)) AS jobsList
from Candidate2 C
outer APPLY (select top 1 CH.CandiateId, CH.ResultStatusText , CH.TimeStamp , CH.notes
from CandidateCallHistory CH
where CH.CandiateId = C.Id
order by TimeStamp desc) as Status
where Status.ResultStatusText <> 'completed' and Status.ResultStatusText <> 'canceled' and c.isactive = 1
I have multiple records in the CandidateCallHistory table and seems this is causing issue with the outer apply ( i may be wrong) as it should only get the most recent record in the table since it selects top 1.
Try to add distinct in first line after select:
select distinct [...]
I have 3 tables say Employee, Permanent_Emp and Contract_Emp
SELECT E.EMP_NO,
E.NAME,
JET.EMP_TYPE,
JET.DATE_JOINED
FROM Employee E
LEFT OUTER JOIN
/* Here Join Table Name(JET) it can be Permanent_Emp or Contract_Emp
which i want as a result of my case expression. */
ON (some condition here) ORDER BY E.EMP_NO DESC
case expression:
CASE
WHEN (E.EMP_TYPE_CODE >10 )
THEN
Permanent_Emp JET
ELSE
Contract_Emp JET
END
Note: table and column names are just for an example to understand requirement.
how can i have join table name from a case expression?
Something like this (although without a description of your tables, the exact join conditions or any sample data its hard to give a more precise answer):
SELECT E.EMP_NO,
E.NAME,
COALESCE( P.EMP_TYPE, C.EMP_TYPE ) AS EMP_TYPE
COALESCE( P.DATE_JOINED, C.DATE_JOINED ) AS DATE_JOINED
FROM Employee E
LEFT OUTER JOIN
Permanent_Emp P
ON ( E.EMP_TYPE_CODE > 10 AND E.EMP_NO = P.EMP_NO )
LEFT OUTER JOIN
Contract_Emp C
ON ( E.EMP_TYPE_CODE <= 10 AND E.EMP_NO = C.EMP_NO )
ORDER BY
E.EMP_NO DESC
use your case in select and join both tables
as
SELECT case when 1 then a.column
when 2 then b.column
end
from table c
join table a
on 1=1
join table2 b
on 1=1
but you cant use case while joining. its better to join both tables and in select use case statement with conditions as per your requirement
There is no way to conditionally add tables to a query in static SQL. If the relevant columns in Permanent_Emp and Contract_Emp are roughly equivalent, you could use a union in a sub-query.
SELECT *
FROM employee e
JOIN
(SELECT employee_id, relevant_column, 'P' AS source_indicator
FROM permanent_emp
UNION ALL
SELECT employee_id, relevant_column, 'C' AS source_indicator
FROM contract_emp) se
ON e.employee_id = se.employee_id
AND ( (e.emp_type_code > 10 AND source_indicator = 'P')
OR (e.emp_type_code <= 10 AND source_indicator = 'C'))
Using Alan's query as a starting point you can still use a case statement, just move it to the join condition:
SELECT *
FROM employee e
JOIN (
SELECT employee_id
, relevant_column
, 'P' AS source_indicator
FROM permanent_emp
UNION ALL
SELECT employee_id
, relevant_column
, 'C' AS source_indicator
FROM contract_emp
) se
ON se.employee_id = e.employee_id
and se.source_indicator = case when e.emp_type_code > 10
then 'P'
else 'C'
end
The only difference between this query and Allan's is the use of a case statement instead of an or statement.
I'm generating a data set that looks like this
category user total
1 jonesa 0
2 jonesa 0
3 jonesa 0
1 smithb 0
2 smithb 0
3 smithb 5
1 brownc 2
2 brownc 3
3 brownc 4
Where a particular user has 0 records in all categories is it possible to remove their rows form the set? If a user has some activity like smithb does, I'd like to keep all of their records. Even the zeroes rows. Not sure how to go about that, I thought a CASE statement may be of some help but I'm not sure, this is pretty complicated for me. Here is my query
SELECT DISTINCT c.category,
u.user_name,
CASE WHEN (
SELECT COUNT(e.entry_id)
FROM category c1
INNER JOIN entry e1
ON c1.category_id = e1.category_id
WHERE c1.category_id = c.category_id
AND e.user_name = u.user_name
AND e1.entered_date >= TO_DATE ('20140625','YYYYMMDD')
AND e1.entered_date <= TO_DATE ('20140731', 'YYYYMMDD')) > 0 -- I know this won't work
THEN 'Yes'
ELSE NULL
END AS TOTAL
FROM user u
INNER JOIN role r
ON u.id = r.user_id
AND r.id IN (1,2),
category c
LEFT JOIN entry e
ON c.category_id = e.category_id
WHERE c.category_id NOT IN (19,20)
I realise the case statement won't work, but it was an attempt on how this might be possible. I'm really not sure if it's possible or the best direction. Appreciate any guidance.
Try this:
delete from t1
where user in (
select user
from t1
group by user
having count(distinct category) = sum(case when total=0 then 1 else 0 end) )
The sub query can get all the users fit your removal requirement.
count(distinct category) get how many category a user have.
sum(case when total=0 then 1 else 0 end) get how many rows with activities a user have.
There are a number of ways to do this, but the less verbose the SQL is, the harder it may be for you to follow along with the logic. For that reason, I think that using multiple Common Table Expressions will avoid the need to use redundant joins, while being the most readable.
-- assuming user_name and category_name are unique on [user] and [category] respectively.
WITH valid_categories (category_id, category_name) AS
(
-- get set of valid categories
SELECT c.category_id, c.category AS category_name
FROM category c
WHERE c.category_id NOT IN (19,20)
),
valid_users ([user_name]) AS
(
-- get set of users who belong to valid roles
SELECT u.[user_name]
FROM [user] u
WHERE EXISTS (
SELECT *
FROM [role] r
WHERE u.id = r.[user_id] AND r.id IN (1,2)
)
),
valid_entries (entry_id, [user_name], category_id, entry_count) AS
(
-- provides a flag of 1 for easier aggregation
SELECT e.[entry_id], e.[user_name], e.category_id, CAST( 1 AS INT) AS entry_count
FROM [entry] e
WHERE e.entered_date BETWEEN TO_DATE('20140625','YYYYMMDD') AND TO_DATE('20140731', 'YYYYMMDD')
-- determines if entry is within date range
),
user_categories ([user_name], category_id, category_name) AS
( SELECT u.[user_name], c.category_id, c.category_name
FROM valid_users u
-- get the cartesian product of users and categories
CROSS JOIN valid_categories c
-- get only users with a valid entry
WHERE EXISTS (
SELECT *
FROM valid_entries e
WHERE e.[user_name] = u.[user_name]
)
)
/*
You can use these for testing.
SELECT COUNT(*) AS valid_categories_count
FROM valid_categories
SELECT COUNT(*) AS valid_users_count
FROM valid_users
SELECT COUNT(*) AS valid_entries_count
FROM valid_entries
SELECT COUNT(*) AS users_with_entries_count
FROM valid_users u
WHERE EXISTS (
SELECT *
FROM user_categories uc
WHERE uc.user_name = u.user_name
)
SELECT COUNT(*) AS users_without_entries_count
FROM valid_users u
WHERE NOT EXISTS (
SELECT *
FROM user_categories uc
WHERE uc.user_name = u.user_name
)
SELECT uc.[user_name], uc.[category_name], e.[entry_count]
FROM user_categories uc
INNER JOIN valid_entries e ON (uc.[user_name] = e.[user_name] AND uc.[category_id] = e.[category_id])
*/
-- Finally, the results:
SELECT uc.[user_name], uc.[category_name], SUM(NVL(e.[entry_count],0)) AS [entry_count]
FROM user_categories uc
LEFT OUTER JOIN valid_entries e ON (uc.[user_name] = e.[user_name] AND uc.[category_id] = e.[category_id])
Here's another method:
WITH totals AS (
SELECT
c.category,
u.user_name,
COUNT(e.entry_id) AS total,
SUM(COUNT(e.entry_id)) OVER (PARTITION BY u.user_name) AS user_total
FROM
user u
INNER JOIN
role r ON u.id = r.user_id
CROSS JOIN
category c
LEFT JOIN
entry e ON c.category_id = e.category_id
AND u.user_name = e.user_name
AND e1.entered_date >= TO_DATE ('20140625', 'YYYYMMDD')
AND e1.entered_date <= TO_DATE ('20140731', 'YYYYMMDD')
WHERE
r.id IN (1, 2)
AND c.category_id IN (19, 20)
GROUP BY
c.category,
u.user_name
)
SELECT
category,
user_name,
total
FROM
totals
WHERE
user_total > 0
;
The totals derived table calculates the totals per user and category as well as totals across all categories per user (using SUM() OVER ...). The main query returns only rows where the user total is greater than zero.
For each row from table tClass matching a given where clause,
join on the first row in tEv, sorted by time, where tEv.class_id = tClass.class_id
The following code throws the error
ORA-01799: a column may not be outer-joined to a subquery
select
c.class_id,
c.class_name,
e.start_time,
e.ev_id
from
tClass c
left join tEv e on (
e.ev_id = (
select
ss1.ev_id
from (
select
ed.ev_id
from
tEvDisp ed,
tEv e
where
ed.class_id = c.class_id
and ed.viewable = 'Y'
and ed.display_until > localtimestamp
and e.ev_id = ed.ev_id
order by
e.start_time
) ss1
where
rownum = 1
)
)
where
c.is_matching = 'Y';
How can this be rewritten to do what is described?
The above is for oracle, but needs to work in sqlite (substituting where necessary)
No idea about SQLite - that would need to be a separate question if this doesn't work - but for Oracle you could do something like this:
select c.class_id,
c.class_name,
e.start_time,
e.ev_id
from tClass c
left join (
select class_id, ev_id, start_time
from (
select ed.class_id,
ed.ev_id,
e.start_time,
row_number() over (partition by ed.class_id order by e.start_time) as rn
from tEvDisp ed
join tEv e on e.ev_id = ed.ev_id
where ed.viewable = 'Y'
and ed.display_until > localtimestamp
)
where rn = 1
) e on e.class_id = c.class_id
where c.is_matching = 'Y';
This uses a subquery which finds the most tEv data, using an analytic row_number() to identify the latest data for each class_id, which is restricted by the rn = 1 filter.
That subquery, consisting of at most one row per class_id, is then used the left outer join against tClass.
This sort of construct should get you what you need. You can fix the details.
select c.classid
, c.classname
, temp.maxstarttime
from tClass c left join (
select c.classid id
max(e.start_time) maxstarttime
from tClass join tEv on tEv.classId = tClass.ClassId
where whatever
group by c.classid) temp on c.classid = temp.id
I'm trying to print out the results from the "GermanDB" Database first, while also showing everything from the Boston DB that was not in the German database. Can this be done in one query?
My query (the bold part functions but does not order the way I want)
select * from (
SELECT DISTINCT a.ProductRef
FROM GERMANDB.dbo.LOCATIONS AS a INNER JOIN GERMANDB.dbo.ITEMS AS b ON a.ProductRef = b.ProductRef
WHERE b.ACTIVE=1
) ta
UNION select * from
SELECT DISTINCT c.ProductRef
FROM BOSTONDB.dbo.LOCATIONS AS c INNER JOIN BOSTONDB.dbo.ITEMS AS d ON c.ProductRef = d.ProductRef
WHERE c.ACTIVE=1 (c.ProductRef NOT IN
(SELECT ProductRef FROM GERMANDB.dbo.ITEMS where ACTIVE=1))
) tb
order by ta.ProductRef** , tb.productRef
Just add one field to signal the priority. Like this:
select *, 0 as Priority from (
SELECT DISTINCT a.ProductRef
FROM GERMANDB.dbo.LOCATIONS AS a INNER JOIN GERMANDB.dbo.ITEMS AS b ON a.ProductRef = b.ProductRef
WHERE b.ACTIVE=1
) ta
UNION select *, 1 as Priority from
SELECT DISTINCT c.ProductRef
FROM BOSTONDB.dbo.LOCATIONS AS c INNER JOIN BOSTONDB.dbo.ITEMS AS d ON c.ProductRef = d.ProductRef
WHERE c.ACTIVE=1 (c.ProductRef NOT IN
(SELECT ProductRef FROM GERMANDB.dbo.ITEMS where ACTIVE=1))
) tb
order by Priority, ProductRef