Throwing conversion error while pass the value directly - sql

Question

This code throws an error when pass the value directly, but it doesn't show any error if pass the value by using parameter.
--It throws an Error
DECLARE #sql NVARCHAR(4000)
DECLARE #ID INT=1234
SET #sql = N'select
[count]
FROM dbo.Table_1 AS t
JOIN dbo.table_2 AS t2 ON t.store_number = t2.store_number
AND t2.[year] = 17
AND t2.week_of_year = 6
AND t2.day_of_week = 2
WHERE t.RC_ID = #ID'
EXEC sp_executesql #sql
-- It throws an error
select
[count]
FROM dbo.Table_1 AS t
JOIN dbo.table_2 AS t2 ON t.store_number = t2.store_number
AND t2.[year] = 17
AND t2.week_of_year = 6
AND t2.day_of_week = 2
WHERE t.ID = 1234
-- IT WORKS
DECLARE #sql
DECLARE #ID INT
SET #ID = 1234
select
[count]
FROM dbo.Table_1 AS t
JOIN dbo.table_2 AS t2 ON t.store_number = t2.store_number
AND t2.[year] = 17
AND t2.week_of_year = 6
AND t2.day_of_week = 2
WHERE t.ID = #ID
The Error is :
Msg 245, Level 16, State 1, Line 1 Conversion failed when converting
the varchar value 'TEST' to data type int.
But there is No data like 'Test' in the table.

Answer 1

One of your values that you are comparing as integers contains a bad value:
select t2.*
from table_2 t2
where try_convert(int, year) is null or try_convert(int, week_of_year) is null or
try_convert(int, day_of_week) or try_convert(int, id) is null;
Whether the error occurs depends on the execution plan.

Answer 2

from what i see you are trying to use a parameter(#id) into the sp_executeSQL without never passing it. A quick fix would be to do something like that
DECLARE #sql NVARCHAR(4000)
DECLARE #ID INT = 10
SET #sql = N'select
[count]
FROM dbo.Table_1 AS t
JOIN dbo.table_2 AS t2 ON t.store_number = t2.store_number
AND t2.[year] = 17
AND t2.week_of_year = 6
AND t2.day_of_week = 2
WHERE t.RC_ID = ' + cast(#ID as nvarchar(20))
EXEC sp_executesql #sql
Hope this helps

Answer 3

One of your table columns that you are filtering is not a numeric data type. When you do
WHERE VarcharColumn = 1
The SQL Server engine will always try to convert the most complex type to the simplest one, in this case "1" is a integer and VarcharColumn is VARCHAR, so the engine will try to convert all the values stored in VarcharColumn to integer before filtering by value 1. Since at least one value stored there is not an integer ("TEST") then the conversion fails and that message pops up.
You have 2 solutions:
Validate and fix all your values in those columns so they are actually numbers and alter the data type to the corresponding one.
Compare against the same type. WHERE Column = '1'
Of course always try to keep your data types in check.
Also in your dynamicSQL query, the declaration of the #ID must be inside your script (it's also missing an initial value).
DECLARE #sql NVARCHAR(4000)
SET #sql = N'
DECLARE #ID INT = 1
select
[count]
FROM dbo.Table_1 AS t
JOIN dbo.table_2 AS t2 ON t.store_number = t2.store_number
AND t2.[year] = 17
AND t2.week_of_year = 6
AND t2.day_of_week = 2
WHERE t.RC_ID = #ID'
EXEC sp_executesql #sql
The reason for the error poping up 'sometimes' is because the different forms of your statement are making the execution plan do things in different order. If it tries to convert the varchar value to int first, it will fail. If it tries to convert the int value to varchar (for example) then it won't fail.
To find the problem, try this:
SELECT
*
FROM
dbo.Table_1 AS T
WHERE
CONVERT(VARCHAR(200), T.store_number) = 'Test' OR
CONVERT(VARCHAR(200), T.ID) = 'Test'
SELECT
*
FROM
dbo.table_2 AS T
WHERE
CONVERT(VARCHAR(200), T.store_number) = 'Test' OR
CONVERT(VARCHAR(200), T.[year]) = 'Test' OR
CONVERT(VARCHAR(200), T.week_of_year) = 'Test' OR
CONVERT(VARCHAR(200), T.day_of_week) = 'Test'