What is wrong with this access query? - sql

Question

Running the below query returns 0 records, but I would expect it to return 3.
SELECT
ID,
DW2_TV_DimStation_Id,
DW2_OTT_DimStation_Id,
Name,
CoreTVCode,
CoreOTTCode,
StrataTVCode,
HouseHolds,
MaleSkew,
FemaleSkew,
AverageAge,
AverageIncome,
BroadReach,
Description,
Owner,
Notes,
timestamp,
CreatedOn,
ModifiedOn,
Retired,
1 AS Accepted
FROM
Planning_DimStation AS src
WHERE
src.[timestamp] = (
SELECT
MAX([timestamp])
FROM
Planning_DimStation AS src2
WHERE
src2.[ID] = src.[ID]
)
AND NOT EXISTS (
SELECT
1
FROM
DimStation AS tgt
WHERE
tgt.[ID] = src.[ID]
);
The part that breaks it is the NOT EXISTS statement. If I delete the NOT EXISTS it works fine.
Table 1: Planning_DimStation
Is an SQL table linked with 3 records in it. Source below.
Table 2: DimStation
Is an Access table (pic of source UI below) that is empty
Could this be a silent fail caused by type missmatch?
Table 1:
CREATE TABLE [Planning].[DimStation]
(
[ID] INT PRIMARY KEY,
[DW2_TV_DimStation_Id] INT NULL,
[DW2_OTT_DimStation_Id] INT NULL,
[Name] NVARCHAR(128) NOT NULL,
[CoreTVCode] CHAR(5) NULL,
[CoreOTTCode] CHAR(10) NULL,
[StrataTVCode] CHAR(10) NULL,
[HouseHolds] DECIMAL(5,2) NULL,
[MaleSkew] DECIMAL(5,2) NULL,
[FemaleSkew] DECIMAL(5,2) NULL,
[AverageAge] INT NULL,
[AverageIncome] DECIMAL(23,2) NULL,
[BroadReach] BIT NULL,
[Description] NVARCHAR(MAX) NULL,
[Owner] NVARCHAR(128) NULL,
[Notes] NVARCHAR(MAX) NULL,
[timestamp] timestamp NOT NULL,
[CreatedOn] DATETIME2(7) CONSTRAINT [df_Planning_DimStation_CreatedOn] DEFAULT (sysutcdatetime()) NOT NULL,
[ModifiedOn] DATETIME2(7) CONSTRAINT [df_Planning_DimStation_ModifiedOn] DEFAULT (sysutcdatetime()) NOT NULL,
[Retired] BIT CONSTRAINT [df_Planning_DimStation_Retired] DEFAULT (0) NOT NULL
)
GO
Table 2:

Answer 1

Joining on different data types tends to yield unexpected results.
To fix this, use casts.
A note is that Access doesn't allow nulls to be cast. So we need to work around that using Nz (same as ISNULL in T-SQL) and explicitly handling nulls.
AND NOT EXISTS (
SELECT
1
FROM
DimStation AS tgt
WHERE
CLng(IIF(tgt.[ID] IS NULL, 0, tgt.ID)) = src.[ID] AND NOT tgt.ID IS NULL
);