Select #variable not working - sql

Question

I can't seem to wrap my mind around a little situation I have. I am trying to set a variable using an if condition; I have also tried using a case statement as well, but keep receiving error. Below is what I am working with and it's dynamic SQL as well... The variable I am trying to set is #EBP_Allow... Can someone shine some light on this?
What I need it to do for example...
SELECT
#EBP_Allow = IF #Year > 2014 THEN DO a SELECT ELSE DO Something else...
What I have now...
SELECT
#OU_Allow = Optional_Unit_Allowed_Flag,
#BU_Allow = Basic_Unit_Allowed_Flag,
#EU_Allow = Enterprise_Unit_Allowed_Flag,
#WU_Allow = Whole_Farm_Unit_Allowed_Flag,
#EBP_Allow = I NEED TO USE SUB SELECT, IF OR CASE TO SET THIS
FROM dbo.#YEAR_Insurance_Offer
WHERE
(dbo.#YEAR_Insurance_Offer.State_Code = #StateCode) AND
(dbo.#YEAR_Insurance_Offer.County_Code = #CountyCode) AND
(dbo.#YEAR_Insurance_Offer.Crop_Code = ''#CropCode'') AND
(dbo.#YEAR_Insurance_Offer.Insurance_Plan_ID = #PlanId) #TypeCondition #PracticeCondition
Here's an update; it seems that when ran it's still jumping over my condition...
CASE
WHEN #YEAR < 2015
THEN ''N''
WHEN #YEAR > 2014
THEN (
SELECT Enterprise_Unit_By_Practice_Allowed_Flag
FROM dbo.#YEAR_Insurance_Offer
WHERE
(dbo.#YEAR_Insurance_Offer.State_Code = #StateCode) AND
(dbo.#YEAR_Insurance_Offer.County_Code = #CountyCode) AND
(dbo.#YEAR_Insurance_Offer.Crop_Code = ''#CropCode'') AND
(dbo.#YEAR_Insurance_Offer.Insurance_Plan_ID = #PlanId) #TypeCondition #PracticeCondition
)
END
If I replace the WHEN #Year > 2014 with this...
WHEN #YEAR > 2014
THEN ''N''
It work's just fine... For some reason or another when I have the select in there it's telling me that Enterprise_Unit_By_Practice_Allowed_Flag is an invalid column, but it's not?

Answer 1

In order to set #EPB_Allow you can use a CASE statement and you can add multiple WHEN clauses to treat different situations:
SELECT
#OU_Allow = Optional_Unit_Allowed_Flag,
#BU_Allow = Basic_Unit_Allowed_Flag,
#EU_Allow = Enterprise_Unit_Allowed_Flag,
#WU_Allow = Whole_Farm_Unit_Allowed_Flag,
#EBP_Allow = CASE
WHEN #Year > 2014
THEN (SELECT column FROM Table where conditions1...)
WHEN #Year > 2013
THEN (SELECT column FROM Table where conditions2...)
ELSE (SELECT column FROM Table where conditions3...)
END
FROM dbo.#YEAR_Insurance_Offer
WHERE
(dbo.#YEAR_Insurance_Offer.State_Code = #StateCode) AND
(dbo.#YEAR_Insurance_Offer.County_Code = #CountyCode) AND
(dbo.#YEAR_Insurance_Offer.Crop_Code = ''#CropCode'') AND
(dbo.#YEAR_Insurance_Offer.Insurance_Plan_ID = #PlanId)
#TypeCondition #PracticeCondition
Also, make sure that if you have defined #EBP_Allow as NVARCHAR then you have to make sure that the datatype returned by the query which selects what value you want to assign the variable is of the same datatype (otherwise use conversion functions).
And you have to make sure that the query that you specify in the THEN part will return only one result.

Answer 2

OK first it seems you have fallen into the horrible practice of creating new tables with each year. This is a huge database antipattern and if this is the first year you have done this, I suggest an immediate redesign as this just gets harder and harder to deal with as you add more years.
If you can't, well then at least learn from this and never allow anyone to design a table like this in the future. In enterprise level datbase you can partition by date and in smaller ones, you dont need to have differnt tables just a where clause to filter by year and good indexing.
But you seem to be stuck using dynamic SQL to do everything (another reason why this is a horrible design choice). So you might as well learn how to use dynamic SQl correctly.
First read and thorughly understand this link before you try to write code against this database design:
http://www.sommarskog.se/dynamic_sql.html
Here is an example below of how you build and view the generated SQl for a dynamic SQl statement. This will help you corretly build the statement before you try to execute it.
declare #SQl nvarchar (max), #year nchar (4) = '2014'
set #sql = 'SELECT Enterprise_Unit_By_Practice_Allowed_Flag
FROM dbo.' +#YEAR+ '_Insurance_Offer
WHERE dbo.'+ #YEAR + '_Insurance_Offer.State_Code = #StateCode'
Print #sql
Since you are doing this in Stored procs, all of them should be designed with a debug variable that is used to display any SQL built. It doesn't need to run in the debug mode in prodcution, but when you have a problem (and you can't possibly forsee every variable that will ever be part of creating a dynamic sql statement and there is close to a 100% probability that you will encounter wierd bugs that you have to troubleshoot later. So you need to build in troubleshooting ability into every proc you write with dynamic SQl.
Of course to execute you need to learn to use sp_executesql.
But really read the link, share the link with your managers and coworkers and think about better ways to do this.

Answer 3

dbo.#YEAR_Insurance_Offer.State_Code
[databaseowner].[table].[fieldname]
Table name as variable
According to this table names need to be static.
Honestly, I have never seen a variable table name. Further, I can't think of a good reason to do this. So this is either a logic error or a syntax error?