Power Query - How to pass blank Excel cell as NULL value? - excel

Question

I have SQL that looks like this, which works fine in SSMS:
DECLARE #pPart VARCHAR(100) = '00039',
#pColor VARCHAR(100) = '01816'
SET #pPart = ISNULL(#pPart,'-1')
SET #pColor = ISNULL(#pColor,'-1')
SELECT *
FROM myTable
WHERE (PartID IN (SELECT (#pPart)) OR #pPart = '-1')
AND (ColorID IN (SELECT (#pColor)) OR #pColor = '-1')
If I change either value (or both values) in the DECLARE from a value to NULL, the code returns the results I expect. I'm just not sure how to make this work within Power Query. If both cells are populated with values, the query works. If I delete the value from either cell, it's just returning a list of all the tables in my database (weird...).
I created a named range called "GetValues" that covers B2:B3 and looks like this:
Name
Value
Part
00039
Color
01816
In the Advanced Editor of Power Query, my query looks like this:
let
Source = Excel.CurrentWorkbook(){[Name="GetValues"]}[Content],
pPart = Source{1}[Column1],
pColor = Source{2}[Column1],
Query = "
DECLARE #pPart VARCHAR(100) = '"& pPart &"',
#pColor VARCHAR(100) = '"& pColor &"'
SET #pPart = ISNULL(#pPart,'-1')
SET #pColor = ISNULL(#pColor,'-1')
SELECT *
FROM myTable
WHERE (PartID IN (SELECT (#pPart)) OR #pPart = '-1')
AND (ColorID IN (SELECT (#pColor)) OR #pColor = '-1')
",
Target = Sql.Database("myServer", "myDatabase", [Query=Query])
in
Target
I tried changing my SET lines, which also works in SSMS if I change a value to '' or ' ' but still returns a list of all tables in my DB in Power Query. I'm trimming the strings in case the user put a space in the cells instead of leaving them blank:
IF LTRIM(RTRIM(#pPart)) = '' SET #pPart = '-1'
IF LTRIM(RTRIM(#pColor)) = '' SET #pColor = '-1'
So how do I pass a blank cell as NULL or at least as '' ?
EDIT: I also tried stripping my query down to the bare bones to see what parameters are being passed. This query successfully returns the value in B2.
let
Source = Excel.CurrentWorkbook(){[Name="GetValues"]}[Content],
pPart = Source{1}[Column1],
Query = "
DECLARE #pPart VARCHAR(100) = '"& pPart &"'
SELECT #pPart
",
Target = Sql.Database("myServer", "myDatabase", [Query=Query])
in
Target
Now I want to see what happens when I include the blank cell B3:
let
Source = Excel.CurrentWorkbook(){[Name="GetValues"]}[Content],
pPart = Source{1}[Column1],
pColor = Source{2}[Column1],
Query = "
DECLARE #pPart VARCHAR(100) = '"& pPart &"',
#pColor VARCHAR(100) = '"& pColor &"'
SELECT #pPart, #pColor
",
Target = Sql.Database("myServer", "myDatabase", [Query=Query])
in
Target
This query also returned a list of all the tables in my database.
I also tried changing
in
Target
to
in
pColor
and the query preview shows null in all lowercase, which makes me think it's indeed returning a null value. I just can't figure out how to make this work.

Answer 1

If the goal is to treat blank cell values as a wildcard then this will work: first remove the SET statements then use this sql:
SELECT *
FROM myTable
WHERE (PartID = #pPart OR #pPart is null OR TRIM(#pPart) ='')
AND (ColorID = #pColor OR #pColor is null OR TRIM(#pColor) ='')
You would get:
Alll rows only if both variables are blank.
No rows if #pPart is not null/blank and has no matches
No rows if #pColor is not null/blank and has no matches
You could add this condition to prevent returning any rows when both inputs are blank/ null:
AND ( ISNULL(TRIM(pPart), '') <> '' OR ISNULL(TRIM(pColor), '') <> '')

Answer 2

To get this to work, I had to address the null values before the query started. For whatever reason (EDIT: Jeroen gives the actual reason in the comment below), passing pPart or pColor as NULL would just return a list of tables and didn't actually pass the NULL value. Here's what seems to be working:
let
Source = Excel.CurrentWorkbook(){[Name="GetValues"]}[Content],
pPart = if Source{1}[Column1] = null then "-1" else Source{1}[Column1],
pColor = if Source{2}[Column1] = null then "-1" else Source{2}[Column1],
Query = "
DECLARE #pPart VARCHAR(100) = '"& pPart &"',
#pColor VARCHAR(100) = '"& pColor &"'
SELECT *
FROM myTable
WHERE (PartID= '" & pPart & "' OR " & pPart & " = '-1')
AND (ColorID = '" & pColor & "' OR " & pColor & " = '-1')
",
Target = Sql.Database("myServer", "myDatabase", [Query=Query])
in
Target