Invalid use of Null VBA Excel - mysql

Question

Please find the below table and code. I am facing Invalid use of Null Error
Table 1
Table 2
VBA code:-
Sub sql()
sql_string = "Select [Sheet1$].[Sr], [Sheet2$].[Name], [Sheet2$].[Value] From [Sheet1$]" & _
" Inner Join [Sheet2$] On CInt([Sheet1$].[Sr]) = CInt(Mid([Sheet2$].[Name],InStr(1,[Sheet2$].[Name],""#"")+1))"
sq = SQL_query(sql_string)
end sub
Function SQL_query(ByRef sql_string As Variant)
Dim cn As ADODB.Connection
Dim rs As ADODB.Recordset
strFile = ThisWorkbook.FullName
strCon = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" & strFile _
& ";Extended Properties=""Excel 12.0;HDR=Yes;IMEX=1"";"
Set cn = CreateObject("ADODB.Connection")
Set rs = CreateObject("ADODB.Recordset")
cn.Open strCon
strSQL = sql_string
rs.Open strSQL, cn
Sheet5.Range("A21").CopyFromRecordset rs ''HERE I AM FACING ERROR
End Function
Please guide me.. on my below error.
In table2 column Sr after # there are some number's which is similar to table1 column Sr number's.I want to do inner join as per that particular number.
required output.

Answer 1

Start by writing Option Explicit on top of the module. Why does my code run without 'Option Explicit' but fail with it?
Then change the Sub sql() to something like this:
Function sql_string() as string
sql_string = "Select [Sheet1$].[Sr], [Sheet2$].[Name], [Sheet2$].[Value] From [Sheet1$]" & _
" Inner Join [Sheet2$] On CInt([Sheet1$].[Sr]) = CInt(Mid([Sheet2$].[Name],InStr(1,[Sheet2$].[Name],""#"")+1))"
end sub
In the immediate window, write ?sql_string and see what you get.
Find a way to test what you get