How do I translate this into ecto?
SELECT *
FROM mytable
WHERE (url,"when") IN
( SELECT url, MAX("when")
FROM mytable
GROUP BY url
)
it works fine in postgresql shell, but I get a Ecto.QueryError at runtime:
subquery must return a single field in order to be used on the right-side of `in` in query
from this code:
subq =
from(f in MyTable,
select: [f.url, max(f.when)],
group_by: f.url
)
from(s in MyTable,
where: [s.url, s.when] in subquery(subq)
)
Related
I have a C# app. It uses EntityFramework.6.2.0 to access a DB in SQL Server 2012.
I need to execute in the app a following query using LINQ to SQL:
Tables used by the query:
CREATE TABLE [Work.Work] (
[WorkCode] INT IDENTITY (1, 1) NOT NULL
)
The 2nd table is a child of [Work.Work]; several its rows correspond to a [Work.Work] row:
CREATE TABLE [Work.WorkContributor] (
[WorkContributorID] INT IDENTITY (1, 1) NOT NULL,
[WorkCode] INT NOT NULL,
[MechanicalShare] DECIMAL (9, 4) NOT NULL,
)
The query (on T-SQL):
select * from [Work.Work] w
CROSS APPLY (select isnull(sum(wc.MechanicalShare), 0) as Sum from [Work.WorkContributor] wc
where wc.WorkCode = w.WorkCode
) subQuery
where subQuery.Sum between 99.9 and 100.1
I need to create an analogue of this SQL query using LINQ to SQL.
I have managed to create an LINQ to SQL code with TWO sub-queries to child [Work.WorkContributor] rows with calculation of SUM(wc.MechanicalShare). The result of the 1st sub-query I compare ‘>= 99.9’. The result of the 2nd sub-query I compare ‘<=100.1’.
Here it is:
var works = entityFrameworkContextObject.Work_Work.AsNoTracking();
works = from w in works
where ((99.9m < (from wc in w.Work_WorkContributor
select new
{
toSum = wc.MechanicalShare
}
).Select(x => x.toSum).Sum()
)
&&
(100.1m > (from wc in w.Work_WorkContributor
select new
{
toSum = wc.MechanicalShare
}
).Select(x => x.toSum).Sum()
)
)
select w;
Yes, it works – but a real SQL query to the DB has TWO separate sub-queries to [Work.WorkContributor]. It will work slow.
Here is the real SQL query:
SELECT
[Project2].[WorkCode] AS [WorkCode]
FROM ( SELECT
[Project1].[WorkCode] AS [WorkCode],
[Project1].[C1] AS [C1],
(SELECT
SUM([Extent3].[MechanicalShare]) AS [A1]
FROM [dbo].[Work.WorkContributor] AS [Extent3]
WHERE [Project1].[WorkCode] = [Extent3].[WorkCode]) AS [C2]
FROM ( SELECT
[Extent1].[WorkCode] AS [WorkCode],
(SELECT
SUM([Extent2].[MechanicalShare]) AS [A1]
FROM [dbo].[Work.WorkContributor] AS [Extent2]
WHERE [Extent1].[WorkCode] = [Extent2].[WorkCode]) AS [C1]
FROM [dbo].[Work.Work] AS [Extent1]
) AS [Project1]
) AS [Project2]
WHERE (99.9 < [Project2].[C1]) AND (100.1 > [Project2].[C2])
Can I create a LINQ to SQL code with only one sub-query to [Work.WorkContributor]; and a real SQL query to the DB would have only one such sub-query?
I currently have the following query:
WITH History AS (
SELECT
kz.*,
kz.__$operation AS operation,
map.tran_begin_time as beginT,
map.tran_end_time as endT
FROM cdc.fn_cdc_get_all_changes_dbo_EXT_GeolObject_KategZalezh(sys.fn_cdc_get_min_lsn('dbo_EXT_GeolObject_KategZalezh'), sys.fn_cdc_get_max_lsn(), 'all') AS kz
INNER JOIN [cdc].[lsn_time_mapping] map
ON kz.[__$start_lsn] = map.start_lsn
where kz.GUID_BalanceHC_Zalezh = 'DDA9AB3A-A0AF-4623-9362-0000C8C83D63'
),
UnpivotedValues AS(
SELECT guid, GUID_another, field, val, operation, beginT, endT
FROM History
UNPIVOT ( [val] FOR field IN
(
area,
oilwidthmin,
oilwidthmax,
efectivwidthmin,
efectivwidthmax,
etc...
))t
),
UnpivotedWithLastValue AS (
SELECT
*,
--Use LAG() to get the last value for the same field
LAG(val, 1) OVER (PARTITION BY guid, GUID_another, field ORDER BY BeginT) LastVal
FROM UnpivotedValues
)
SELECT * FROM UnpivotedWithLastValue WHERE val <> LastVal OR LastVal IS NULL ORDER BY guid
This query returns the changed values for a single table that has CDC (Change Data Capture) enabled.
I want to create a stored procedure that receives the columns to be unpivoted, and the cdc function (e.g. cdc.fn_cdc_get_all_...) as parameters and returns the result set.
The result for this tables must be joined in one report.
In my case parameter 1 is cdc.fn_cdc_get_all_changes_dbo_EXT_GeolObject_KategZalezh(sys.fn_cdc_get_min_lsn('dbo_EXT_GeolObject_KategZalezh'), sys.fn_cdc_get_max_lsn(), 'all'). This is the CDC function.
How should I send the list of fields that i want in the result? How's the string?
Also, is there a way to do without dynamic SQL? Dynamic SQL it is not better solution for performance.
As you know SQL Server is declarative by design and does not support macro substitution.
UNPIVOT would clearly be more performant, but here is a simplified example of a UNPIVOT which does not require Dynamic SQL, but only a little XML.
Example
Let's assume your table/results looks like this:
You may notice that I only we only specify key fields to EXCLUDE in the final WHERE
Declare #YourData table (ID int,Active bit,First_Name varchar(50),Last_Name varchar(50),EMail varchar(50),Salary decimal(10,2))
Insert into #YourData values
(1,1,'John','Smith','john.smith#email.com',85600),
(2,0,'Jane','Doe' ,'jane.doe#email.com',83200)
;with cte as (
-- Replace with your Complex Query
Select * from #YourData
)
Select A.ID
,A.Active
,C.*
From cte A
Cross Apply (Select XMLData=cast((Select A.* for XML RAW) as xml)) B
Cross Apply (
Select Item = attr.value('local-name(.)','varchar(100)')
,Value = attr.value('.','varchar(max)')
From XMLData.nodes('/row') C1(n)
Cross Apply C1.n.nodes('./#*') C2(attr)
Where attr.value('local-name(.)','varchar(100)') not in ('ID','Active')
) C
Returns
If I try to UNION (or INTERSECT or EXCEPT) a common table expression I get a syntax error near the UNION. If instead of using the CTE I put the query into the union directly, everything works as expected.
I can work around this but for some more complicated queries using CTEs makes things much more readable. I also just don't like not knowing why something is failing.
As an example, the following query works:
SELECT *
FROM
(
SELECT oid, route_group
FROM runs, gpspoints
WHERE gpspoints.oid = runs.start_point_oid
UNION
SELECT oid, route_group
FROM runs, gpspoints
WHERE gpspoints.oid = runs.end_point_oid
) AS allpoints
;
But this one fails with:
ERROR: syntax error at or near "UNION"
LINE 20: UNION
WITH
startpoints AS
(
SELECT oid, route_group
FROM runs, gpspoints
WHERE gpspoints.oid = runs.start_point_oid
),
endpoints AS
(
SELECT oid, route_group
FROM runs, gpspoints
WHERE gpspoints.oid = runs.end_point_oid
)
SELECT *
FROM
(
startpoints
UNION
endpoints
) AS allpoints
;
The data being UNIONed together is identical but one query fails and the other does not.
I'm running PostgreSQL 9.3 on Windows 7.
The problem is because CTEs are not direct text-substitutions and a UNION b is invalid SELECT syntax. The SELECT keyword is a mandatory part of the parsing and the syntax error is raised before the CTEs are even taken into account.
This is why
SELECT * FROM a
UNION
SELECT * FROM b
works; the syntax is valid, and then the CTEs (represented by a and b) are then used at the table-position (via with_query_name).
At least in SQL Server, I can easily do this - create two CTE's, and do a SELECT from each, combined with a UNION:
WITH FirstNames AS
(
SELECT DISTINCT FirstName FROM Person
), LastNames AS
(
SELECT DISTINCT LastName FROM Person
)
SELECT * FROM FirstNames
UNION
SELECT * FROM LastNames
Not sure if this works in Postgres, too - give it a try!
I have a nested select query that is returning the proper amount of rows. The query builds a recordset and compares it to a table and returns the records in the query that are not in the table.
I converted the select query to an update query. I am trying to populate the table with the rows returned from the query. When I run the update query it is returning with zero rows to update. I dont understand why because the select query is returning record and I am using the same code in the update query.
Thanks
Select Query: (This is returning several records)
Select *
From
(SELECT DISTINCT
ProductClass,SalProductClass.[Description],B.Branch,B.BranchDesc,B.Salesperson,B.Name,
CAST(0 AS FLOAT) AS Rate,'N' AS Split
FROM (SELECT SalBranch.Branch,SalBranch.[Description] AS BranchDesc,A.Salesperson,A.Name
FROM (SELECT DISTINCT
Salesperson,Name
FROM SalSalesperson
) A
CROSS JOIN SalBranch
) B
CROSS JOIN SalProductClass
) C
Left Outer Join RateComm On
RateComm.ProductClass = C.ProductClass and
RateComm.Branch = C.Branch And RateComm.Salesperson = C.Salesperson
Where RateComm.ProductClass is Null
Update Query: (This is returning zero records)
UPDATE RateComm
SET RateComm.ProductClass=C.ProductClass,RateComm.ProdClassDesc=C.ProdClassDesc,
RateComm.Branch=C.Branch,RateComm.BranchDesc=C.BranchDesc,RateComm.Salesperson=C.Salesperson,
RateComm.Name=C.Name,RateComm.Rate=C.Rate,RateComm.Split=C.Split
FROM (SELECT DISTINCT
ProductClass,SalProductClass.[Description] AS ProdClassDesc,B.Branch,B.BranchDesc,B.Salesperson,B.Name,
CAST(0 AS FLOAT) AS Rate,'N' AS Split
FROM (SELECT SalBranch.Branch,SalBranch.[Description] AS BranchDesc,A.Salesperson,A.Name
FROM (SELECT DISTINCT
Salesperson,Name
FROM SalSalesperson
) A
CROSS JOIN SalBranch
) B
CROSS JOIN SalProductClass
) C
LEFT OUTER JOIN RateComm ON C.ProductClass=RateComm.ProductClass AND
C.Salesperson=RateComm.Salesperson AND C.Branch=RateComm.Branch
WHERE RateComm.ProductClass IS NULL
It's difficult to update what doesn't exist. Have you tried an INSERT query instead?
I'm making select with a union.
SELECT * FROM table_1
UNION
SELECT * FROM table_2
Is it possible to filter query results by column values?
Yes, you can enclose your entire union inside another select:
select * from (
select * from table_1 union select * from table_2) as t
where t.column = 'y'
You have to introduce the alias for the table ("as t"). Also, if the data from the tables is disjoint, you might want to consider switching to UNION ALL - UNION by itself works to eliminate duplicates in the result set. This is frequently not necessary.
A simple to read solution is to use a CTE (common table expression). This takes the form:
WITH foobar AS (
SELECT foo, bar FROM table_1
UNION
SELECT foo, bar FROM table_2
)
Then you can refer to the CTE in subsequent queries by name, as if it were a normal table:
SELECT foo,bar FROM foobar WHERE foo = 'value'
CTEs are quite powerful, I recommend further reading here
One tip that you will not find in that MS article is; if you require more than one CTE put a comma between the expression statements. eg:
WITH foo AS (
SELECT thing FROM place WHERE field = 'Value'
),
bar AS (
SELECT otherthing FROM otherplace WHERE otherfield = 'Other Value'
)
If you want to filter the query based on some criteria then you could do this -
Select * from table_1 where table_1.col1 = <some value>
UNION
Select * from table_2 where table_2.col1 = <some value>
But, I would say if you want to filter result to find the common values then you can use joins instead
Select * from table_1 inner join table_2 on table_1.col1 = table_2.col1