SQL：如何根据文件扩展名计算出现次数

Question

我有一个查询，该查询返回一列值：

?????? ?? ?????? ??????? ?.?..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

如何计算基于文件扩展名的出现次数？ 在上面的示例中，我们有三行用于xlsx扩展名，两行用于sav扩展名？

Answer 1

尝试这个：

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

仅隔离扩展部分，然后计算出现次数

Answer 2

请试试：

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

Answer 3

尝试这个

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

SQL小提琴

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