使用switch-case语句进行T-SQL更新

Question

I want implement this pseudocode in t-sql

UPDATE Resources SET [Path]= CASE ([Path].Substring([Path].LastIndexOf('.')))
                            WHEN '.jpg' THEN '/image.jpg'
                            WHEN '.png' THEN '/image.jpg'
                            WHEN '.avi' THEN '/video.jpg' 
                            WHEN '.mkv' THEN '/video.jpg'

for it I use this solution

UPDATE Resources SET [Path] = CASE (SUBSTRING([Path], LEN([Path]) - CHARINDEX('.', REVERSE([Path])) + 1, 3))                
                                        WHEN '.jpg' THEN '/image.jpg'
                                        WHEN '.png' THEN '/image.jpg'
                                        WHEN '.avi' THEN '/video.jpg' 
                                        WHEN '.mkv' THEN '/video.jpg'
                                     END

but it is does not return expected result.

Can anyone give me working version please?

Answer 1

UPDATE 
  Resources 
SET
  Path = CASE SUBSTRING(Path, LEN(Path) - CHARINDEX('.', REVERSE(Path)) + 1, 4)
           WHEN '.jpg' THEN '/image.jpg'
           WHEN '.png' THEN '/image.jpg'
           WHEN '.avi' THEN '/video.jpg' 
           WHEN '.mkv' THEN '/video.jpg'
         END

Answer 2

而不是SUBSTRING([Path], LEN([Path]) - CHARINDEX('.', REVERSE([Path])) + 1, 3) ，尝试使用lower(right([Path], 4))

Answer 3

Your read of the extension is wrong, instead try:

SUBSTRING(Path, LEN(Path) - CHARINDEX('.', REVERSE(Path)) + 1, LEN(Path)) 

(Using LEN(Path) as the read length; fine if it overflows the end of the string and allows for n-character extensions)

Answer 4

Try using the ParseName

UPDATE Resources SET [Path] = CASE (Parsename(Path,1))                
                                        WHEN 'jpg' THEN '/image.jpg'
                                        WHEN 'png' THEN '/image.jpg'
                                        WHEN 'avi' THEN '/video.jpg' 
                                        WHEN 'mkv' THEN '/video.jpg'
                                     END

Answer 5

UPDATE Resources SET ThumbnailPath = CASE SUBSTRING(ThumbnailPath, LEN(ThumbnailPath) - CHARINDEX('.', REVERSE(ThumbnailPath)) + 1, LEN(ThumbnailPath))             
                    WHEN '.doc'   THEN @root + '/doc.png'
                    WHEN '.docx'  THEN @root + '/doc.png'
                    WHEN '.jpg'   THEN @root + '/image.png'
                    WHEN '.jpeg'  THEN @root + '/image.png'
                    WHEN '.gif'   THEN @root + '/image.png'
                    WHEN '.png'   THEN @root + '/image.png'
                    WHEN '.ppt'   THEN @root + '/ppt.png'
                    WHEN '.pptx'  THEN @root + '/ppt.png'
                    WHEN '.pdf'   THEN @root + '/pdf.png'
                    ELSE               @root + '/other.png'
                 END

thank you I finaly use this

Answer 6

This script will assure that you do not update all rows every time you run the script. It will only update changes.

UPDATE r
SET ThumbnailPath = newvalue
FROM Resources r
cross apply 
(SELECT right(ThumbnailPath, patindex('%_.%', reverse(ThumbnailPath))) T) a                 
cross apply 
(SELECT CASE 
                    WHEN a.T in ('doc','docx' )            THEN @root + '/doc.png' 
                    WHEN a.T in ('jpg','jpeg','gif','png') THEN @root + '/image.png' 
                    WHEN a.T in ('ppt','pptx')             THEN @root + '/ppt.png' 
                    WHEN a.T = 'pdf'                       THEN '/pdf.png'
                    ELSE @root + '/other.png' 
                 END newvalue)  b
WHERE r.ThumbnailPath <> b.newvalue