What does a column assignment using an aggregate in the columns area of a select do? - tsql

I'm trying to decipher another programmer's code who is long-gone, and I came across a select statement in a stored procedure that looks like this (simplified) example:
SELECT #Table2.Col1, Table2.Col2, Table2.Col3, MysteryColumn = CASE WHEN y.Col3 IS NOT NULL THEN #Table2.MysteryColumn - y.Col3 ELSE #Table2.MysteryColumn END
INTO #Table1
FROM #Table2
LEFT OUTER JOIN (
SELECT Table3.Col1, Table3.Col2, Col3 = SUM(#Table3.Col3)
FROM Table3
INNER JOIN #Table4 ON Table4.Col1 = Table3.Col1 AND Table4.Col2 = Table3.Col2
GROUP BY Table3.Col1, Table3.Col2
) AS y ON #Table2.Col1 = y.Col1 AND #Table2.Col2 = y.Col2
WHERE #Table2.Col2 < #EnteredValue
My question, what does the fourth column of the primary selection do? does it produce a boolean value checking to see if the values are equal? or does it set the #Table2.MysteryColumn equal to some value and then inserts it into #Table1? Or does it just update the #Table2.MysteryColumn and not output a value into #Table1?
This same thing seems to happen inside of the sub-query on the third column, and I am equally at a loss as to what that does as well.


MysteryColumn = gives the expression a name also called a column alias. The fact that a column in the table#2 also has the same name is besides the point.
Since it uses INTO syntax it also gives the column its name in the resulting temporary table. See the SELECT CLAUSE and note | column_alias = expression and the INTO CLAUSE

Related

How to reference a column in the select clause in the order clause in SQLAlchemy like you do in Postgres instead of repeating the expression twice

In Postgres if one of your columns is a big complicated expression you can just say ORDER BY 3 DESC where 3 is the order of the column where the complicated expression is. Is there anywhere to do this in SQLAlchemy?

As Gord Thompson observes in this comment, you can pass the column index as a text object to group_by or order_by:
q = sa.select(sa.func.count(), tbl.c.user_id).group_by(sa.text('2')).order_by(sa.text('2'))
serialises to
SELECT count(*) AS count_1, posts.user_id
FROM posts GROUP BY 2 ORDER BY 2
There are other techniques that don't require re-typing the expression.
You could use the selected_columns property:
q = sa.select(tbl.c.col1, tbl.c.col2, tbl.c.col3)
q = q.order_by(q.selected_columns[2]) # order by col3
You could also order by a label (but this will affect the names of result columns):
q = sa.select(tbl.c.col1, tbl.c.col2, tbl.c.col3.label('c').order_by('c')

Single Value Expression in When Then Aggregate Function TSQL

I am trying to map a certain value of a column based on its count on another table. If the count of [Location] i.e a column of IMPORT.DATA_SCRAP table in each row. For now for location static value i.e Utah and Kathmandu is supplied for test purpose only is equal to 1, then only i need to get the result in the select statement i.e only single value expression must be returned but here n rows of table with value is returned.
For. eg. In the below query,total rows of IMPORT.DATA_SCRAP gets returned, i only need the single first row value in my case.
I came to know whether cursor or CTE will acheive my result but i am unable to figure it out.
Here,
select
case
when
((SELECT COUNT(stateName) FROM Location.tblState where stateName = 'Utah')=1)
then (select stateName, CountryName from Location.tblState where stateName= 'Utah')
end as nameof
from IMPORT.DATA_SCRAP
The relation between country, state, city is as below:
select
case
when
((SELECT COUNT(cityName) FROM Location.tblCity where cityName = 'Kathmandu')=1)
then (select ct.countryName from Location.tblCity c
inner join Location.tblState s
on c.stateID = s.StateID
inner join Location.tblCountry ct
on ct.countryId = s.CountryId
where c.cityName = 'Kathmandu'
)
end as nameof
from IMPORT.DATA_SCRAP
How can i return only a single value expresion despite of multiple nmax rows of IMPORT.DATA_SCRAP row in the result.
If i comment out the -- from IMPORT.DATA_SCRAP in the above query i would get the desired single result expression in my case, but unable how can i acheive it in other ways or suggest me the appropriate way to do these types of situation.

postgresql lef join doesn't works

I would like to add to the table A all the column of the table B, doing a join based on a common column (type numeric). I am trying to do it using the LEFT JOIN but the columns added are all blank. this is impossible because table b stores, among others, the same ID values . Where I am wrong?
Select * from "2017_01" left join "Registry_2017" on '2017_01.ID' = 'Registry_2017.ID';

You are doing wrong.. I don't know why you can use right for Table calling "2017_01" and different with this '2017_01.ID'..
' = Single quote identifies as String
" = Double quote identifies as Table or Column to escape Naming
Select
*
From
"2017_01"
left join "Registry_2017" on '2017_01.ID' = 'Registry_2017.ID';
So when you doing this '2017_01.ID' = 'Registry_2017.ID' The condition will always become false because those 2 different String are not equal. Postgresql look the condition not as Table and Column but String because you are using Single quote
Select
*
from
"2017_01"
left join "Registry_2017" on "2017_01"."ID" = "Registry_2017"."ID";
So the query should be like that.. Even you already got answer and it got work i must tell this..

how to select from one table where no matching row in another (but has multiple)

I have tried this:
SELECT *
FROM svc00100
WHERE NOT EXISTS (SELECT *
FROM svc00101
WHERE TECHSTAT = 'INA'
AND svc00100.TECHID = svc00101.TECHID)
I want to select rows from svc00100 but not if there is a row in svc00101 with the same TECHID and with TECHSTAT = 'INA'. But, there are multiple rows in svc00101 with the TECHID matching, some having 'INA' and some having other stuff. I want to eliminate/ignore any TECHID where there is any row in svc00101 with TECHID and 'INA' for techstat. Using SQL server BTW if that helps.

You can use left outer join and Where clause. Like this:
select svc00100.* from svc00100
left outer join svc00101 on TECHSTAT = "INA"
and svc00100.TECHID = svc00101.TECHID
where svc00101.KEY is null
Instead of KEY you should pass name of NOT NULL column. For example Primary Key.

Temporary Table Value into a Table-Value UDF

I was having some trouble with an SQL 2k sproc and which we moved to SQL 2k5 so we could used Table Value UDF's instead of Scalar UDF's.
This is simplified, but this is my problem.
I have a temporary table that I fill up with product information. I then pass that product information into a UDF and return the information back to my main results set. It doesn't seem to work.
Am I not allowed to pass a Temporary Table value into an CROSS APPLY'd Table Value UDF?
--CREATE AND FILL #brandInfo
SELECT sku, upc, prd_id, cp.customerPrice
FROM products p
JOIN #brandInfo b ON p.brd_id=b.brd_id
CROSS APPLY f_GetCustomerPrice(b.priceAdjustmentValue, b.priceAdjustmentAmount, p.Price) cp
--f_GetCUstomerPrice uses the AdjValue, AdjAmount, and Price to calculate users actual price
When I put dummy values in for b.priceAdjustmentValue and b.priceAdjustmentAmount it works great. But as soon as I try to load the temp table values in it bombs.
Msg 207, Level 16, State 1, Line 140
Invalid column name 'b.priceAdjustmentValue'.
Msg 207, Level 16, State 1, Line 140
Invalid column name 'b.priceAdjustmentAmount'.

Have you tried:
--CREATE AND FILL #brandInfo
SELECT sku, upc, prd_id, cp.customerPrice
FROM products p
JOIN #brandInfo b ON p.brd_id=b.brd_id
CROSS APPLY (
SELECT *
FROM f_GetCustomerPrice(b.priceAdjustmentValue, b.priceAdjustmentAmount, p.Price) cp
)
--f_GetCUstomerPrice uses the AdjValue, AdjAmount, and Price to calculate users actual price
Giving the UDF the proper context in order to resolve the column references?
EDIT:
I have built the following UDF in my local Northwind 2005 database:
CREATE FUNCTION dbo.f_GetCustomerPrice(#adjVal DECIMAL(28,9), #adjAmt DECIMAL(28,9), #price DECIMAL(28,9))
RETURNS TABLE
AS RETURN
(
SELECT Level = 'One', AdjustValue = #adjVal, AdjustAmount = #adjAmt, Price = #price
UNION
SELECT Level = 'Two', AdjustValue = 2 * #adjVal, AdjustAmount = 2 * #adjAmt, Price = 2 * #price
)
GO
And referenced it in the following query without issue:
SELECT p.ProductID,
p.ProductName,
b.CompanyName,
f.Level
FROM Products p
JOIN Suppliers b
ON p.SupplierID = b.SupplierID
CROSS APPLY dbo.f_GetCustomerPrice(p.UnitsInStock, p.ReorderLevel, p.UnitPrice) f
Are you certain that your definition of #brandInfo has the priceAdjustmentValue and priceAdjustmentAmount columns defined on it? More importantly, if you are putting this in a stored procedure as you mentioned, does there exist a #brandInfo table already without those columns defined? I know #brandInfo is a temporary table, but if it exists at the time you attempt to create the stored procedure and it lacks the columns, the parsing engine may be getting tripped up. Oddly, if the table doesn't exist at all, the parsing engine simply glides past the missing table and creates the SP for you.