Table-valued function that takes table as parameter and performs join

Question

I use SQL server 2016. I want to write a function that takes a table as a parameter and then performs a join on that table with another table. I have declared the following type:

CREATE TYPE WorklistTable AS TABLE (WorklistId int NOT NULL)

Then I use it in a lot of functions that do selects based on certain conditions

CREATE FUNCTION [dbo].[fnGetSomeData] (
@WorklistIds WorklistTable readonly
)
RETURNS TABLE
    AS RETURN
    (   
    select WorklistId, wlu.UserId
    from @WorklistIds
    join [dbo].[WorklistUser] wlu on wlu.WorklistId = @WorklistIds.worklistId   
    -- the rest is omitted 
);

I get the following error:

Must declare the scalar variable "@WorklistIds".

I tried to declare the variable, but I got an error:

The variable name '@WorklistIds' has already been declared. Variable names must be unique within a query batch or stored procedure.

Answer 1

You should use aliases when you are joing to table variable.

CREATE FUNCTION [dbo].[fnGetSomeData] (
@WorklistIds WorklistTable readonly
)
RETURNS TABLE
    AS RETURN
    (   
    select WorklistId, wlu.UserId
    from @WorklistIds t
    join [dbo].[WorklistUser] wlu on wlu.WorklistId = t.worklistId   
    -- the rest is omitted 
);

Answer 2

You can't directly use the @Table name when referencing a column within a table variable. You either need to alias the table or wrap it in square brackets:

select WorklistId, wlu.UserId
from @WorklistIds As W
join [dbo].[WorklistUser] wlu on wlu.WorklistId = W.worklistId 

Or

select WorklistId, wlu.UserId
from @WorklistIds
join [dbo].[WorklistUser] wlu on wlu.WorklistId = [@WorklistIds].worklistId