Question

As my application is expanding, I now am changing the structure of my database; I now want to control file types within the database. I wanted to start with the current file types already in the database. My Database now has a [simplified] 2 table structure like:

tbFiles: pkFileID, fileType, fileName

tblFileType: pkFileType, typeName, typeDesc

I am trying to have the output of a SELECT query update into the newly created tblFileType table. I have tried among other things:

UPDATE tblFileType
INNER JOIN
(SELECT DISTINCT fileType FROM tblFiles) as X
SET typeName = fileType

but I always seem to get 0 row(s) affected.

When I run

SELECT DISTINCT fileType
FROM  `tblFiles`

I get Showing rows 0 - 22 (~23 total, Query took 0.0074 sec)

I know this must be simple, but why is the UPDATE query not affecting 23 rows?

Answer 1

You need to add a JOIN condition like ON t1.fileType = x.fileType as follows:

UPDATE tblFileType t1
INNER JOIN
(
    SELECT DISTINCT fileType 
    FROM tblFiles
)as X ON t1.fileType = x.fileType
SET t1.typeName = X.fileType

Update: Since the table tblFileType is blank, you will need to use INSERT something like:

INSERT INTO tblFileType(typeName )
SELECT DISTINCT fileType 
FROM tblFiles
WHERE -- a condition here