SQL select查询不起作用。在ms访问2010

Question

here are my two charts and my query. Obviously you do see that some parameter names match. but my query shows up as no results. WHY IS THAT?

Thank you .

Altho this query was made in access 2010 it also works in 2003 and 2007

if you cant read the query in detail. just zoom in on this webpage

UPDATEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE: ****************************8

thanks for all your help but i have solved it my own way. and because im doing this for work i needed it to be done fast and didnt have too much time to dela with why access trim does nto work =( ... i still dunno why.

but altho my source table is big that one did not have trialing spaces. only the parameter table which i had uploaded from another table that was an excel file and 99 rows.

i went back into the orignal excel file. tried a trim there. copy pasted the trimmed column and paste special values to rid of the formula and it still has the space!! is this jsut an error on the trim function or what?

anyways instead i used a =left(cell,len(cell)-1) to rid of the one trailign space

then reuploaded the excel parameter table and now its working. lengthy story but. if anyone has another suggestions on why TRIM doesnt work please explain . i used LTRIM RTRIM. BOTH together and jsut TRIM

Answer 1

In a reply to @flayto you said "*turns out there is one trailing space behind each Parameter_Name value in ParameterTable. But i tried trimming in it does say it updates all of the entries in that table yet the one space sitll does not go away!*"

A few times I have copied a range of cells from an Excel spreadsheet into Access tables. The data in Access included invisible trailing characters after the text I expected. Since those characters were not spaces, they were not removed by the Trim() function. See what you actually have following the Paramater_Name values.

SELECT
    Parameter_Name,
    Len(Parameter_Name) AS Length_of_Parameter_Name
    Asc(Right(Parameter_Name, 1)) AS rightmost_character
FROM ParameterTable;

The fix will depend on what you find. For example, if there is always one and only one unwanted character, you could discard it with this UPDATE statement:

UPDATE Parameter_Table
SET Parameter_Name = Left(Parameter_Name, Len(Parameter_Name) -1);

Whatever UPDATE you try, make sure to backup the database first in case anything goes wrong.

Answer 2

Because you're comparing ParameterTable.Full_Name to T1_SourceTable.Parameter_Name .

You should be comparing ParameterTable.Parameter_Name to T1_SourceTable.Parameter_Name .

***NOTE: I'm leaving this up while I look at this, but I'm suspecting the leading/trailing spaces (as mentioned by a couple of others).

***Possible other solution: Modify this into a specific Inner Join. The links I'm finding from MS don't specifically you can't do what you've done, but they do all use the explicit INNER JOIN Syntax.

So you might try:

SELECT T1.Full_Name, T2.Parameter_Name
FROM ParameterTable T1
INNER JOIN T1_SourceTable T2
  ON T1.Parameter_Name = T2.Parameter_Name

This shouldn't, as far as I know, actually change anything- but, based on the links I'm finding, you might try it out.

Answer 3

Are you sure there are no leading or trailing spaces in the field values? Try wrapping each field with LTRIM/RTRIM as in LTRIM(RTRIM(T1_SourceTable.Parameter_Name)) just to be sure that isn't the problem.

Answer 4

Are they the exact same data type? If not, for Access, try using LIKE instead of equals.

t1.parameter_name like t2.parameter_name

See the example here. http://office.microsoft.com/en-us/access-help/access-sql-where-clause-HA010278156.aspx

Answer 5

If your table is linked and the underlying datatype is char rather than varchar, then it will be blank padding even after you think you have trimmed it. You'll have to change the underlying data type or join on trim(parameter_name) which will be expensive!