SQL：如何根据文件扩展名计算出现次数

Question

I have a query which returns a column of values:

?????? ?? ?????? ??????? ?.?..xlsx
1028-13055 Single Patient Focus Wave 3.sav
2.xlsx
2011 BBQ (13Dec2013).sav
2014 Health IT Purchasing Intentions Survey Results.xlsx
2014 Safety Training and Safety Professionals Survey.sav

How do I count the number of occurrences based on the file extensions? In the above example, we have three rows for the xlsx extension and two for the sav extension?

Answer 1

Try this:

SELECT RIGHT(yourcolumnname,CHARINDEX('.', Reverse(yourcolumnname)) -1)
FROM yourtable

to isolate just the extension part and then count the occurrences

Answer 2

Please try:

SELECT colcnt, 
       Count(*) TotCnt 
FROM  (SELECT RIGHT(col, Charindex('.', Reverse(col)) - 1) ColCnt 
       FROM   yourtable)x 
GROUP  BY colcnt 

Answer 3

Try this

SELECT extension, 
       Count(*) AS ExtensionCount 
FROM   (SELECT RIGHT(name, Charindex('.', Reverse(name)) - 1) AS Extension 
        FROM   files) t 
GROUP  BY extension 

SQL fiddle

http://sqlfiddle.com/#!6/27269/5