Question

我们说我有以下结构：

"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" --build E:\CLion\GLEW-Test\cmake-build-debug --target GLEW_Test -- -j 2
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -HE:\CLion\GLEW-Test -BE:\CLion\GLEW-Test\cmake-build-debug --check-build-system CMakeFiles\Makefile.cmake 0
C:/MinGW/bin/mingw32-make.exe -f CMakeFiles\Makefile2 GLEW_Test
mingw32-make.exe[1]: Entering directory 'E:/CLion/GLEW-Test/cmake-build-debug'
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -HE:\CLion\GLEW-Test -BE:\CLion\GLEW-Test\cmake-build-debug --check-build-system CMakeFiles\Makefile.cmake 0
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -E cmake_progress_start E:\CLion\GLEW-Test\cmake-build-debug\CMakeFiles 2
C:/MinGW/bin/mingw32-make.exe -f CMakeFiles\Makefile2 CMakeFiles/GLEW_Test.dir/all
mingw32-make.exe[2]: Entering directory 'E:/CLion/GLEW-Test/cmake-build-debug'
C:/MinGW/bin/mingw32-make.exe -f CMakeFiles\GLEW_Test.dir\build.make CMakeFiles/GLEW_Test.dir/depend
mingw32-make.exe[3]: Entering directory 'E:/CLion/GLEW-Test/cmake-build-debug'
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -E cmake_depends "MinGW Makefiles" E:\CLion\GLEW-Test E:\CLion\GLEW-Test E:\CLion\GLEW-Test\cmake-build-debug E:\CLion\GLEW-Test\cmake-build-debug E:\CLion\GLEW-Test\cmake-build-debug\CMakeFiles\GLEW_Test.dir\DependInfo.cmake --color=
mingw32-make.exe[3]: Leaving directory 'E:/CLion/GLEW-Test/cmake-build-debug'
C:/MinGW/bin/mingw32-make.exe -f CMakeFiles\GLEW_Test.dir\build.make CMakeFiles/GLEW_Test.dir/build
mingw32-make.exe[3]: Entering directory 'E:/CLion/GLEW-Test/cmake-build-debug'
[ 50%] Linking CXX executable GLEW_Test.exe
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -E cmake_link_script CMakeFiles\GLEW_Test.dir\link.txt --verbose=1
"C:\Program Files\JetBrains\CLion 2017.2.2\bin\cmake\bin\cmake.exe" -E remove -f CMakeFiles\GLEW_Test.dir/objects.a
C:\MinGW\bin\ar.exe cr CMakeFiles\GLEW_Test.dir/objects.a @CMakeFiles\GLEW_Test.dir\objects1.rsp
C:\MinGW\bin\g++.exe  -Wall -Wextra -g   -Wl,--whole-archive CMakeFiles\GLEW_Test.dir/objects.a -Wl,--no-whole-archive  -o GLEW_Test.exe -Wl,--out-implib,libGLEW_Test.dll.a -Wl,--major-image-version,0,--minor-image-version,0 @CMakeFiles\GLEW_Test.dir\linklibs.rsp
CMakeFiles\GLEW_Test.dir/objects.a(main.cpp.obj): In function `main':
E:/CLion/GLEW-Test/main.cpp:8: undefined reference to `_imp__glewInit@0'
E:/CLion/GLEW-Test/main.cpp:12: undefined reference to `_imp__glewGetErrorString@4'
E:/CLion/GLEW-Test/main.cpp:14: undefined reference to `_imp__glewGetString@4'
collect2.exe: error: ld returned 1 exit status
mingw32-make.exe[3]: *** [GLEW_Test.exe] Error 1
CMakeFiles\GLEW_Test.dir\build.make:98: recipe for target 'GLEW_Test.exe' failed
mingw32-make.exe[2]: *** [CMakeFiles/GLEW_Test.dir/all] Error 2
mingw32-make.exe[3]: Leaving directory 'E:/CLion/GLEW-Test/cmake-build-debug'
mingw32-make.exe[1]: *** [CMakeFiles/GLEW_Test.dir/rule] Error 2
CMakeFiles\Makefile2:69: recipe for target 'CMakeFiles/GLEW_Test.dir/all' failed
mingw32-make.exe[2]: Leaving directory 'E:/CLion/GLEW-Test/cmake-build-debug'
CMakeFiles\Makefile2:81: recipe for target 'CMakeFiles/GLEW_Test.dir/rule' failed
mingw32-make.exe[1]: Leaving directory 'E:/CLion/GLEW-Test/cmake-build-debug'
Makefile:120: recipe for target 'GLEW_Test' failed
mingw32-make.exe: *** [GLEW_Test] Error 2

我试图找到date_removed减去date_created的平均数，然后按月分组。

这是我到目前为止所拥有的：

Ticket |date_created       |date_removed

ticket1|2015-05-14 15:08:65|2015-05-11 10:50:11

给出了整个查询的平均天数。我怎么会按月分组呢？

我尝试过以下方法：

select AVG(DATEDIFF(day, date_created, date_resolved)) AS 'avg_days' from 
my_table

但得到了错误：

select AVG(DATEDIFF(day, date_created, date_resolved)) AS 'avg_days', 
MONTH(date_created) AS 'month' from my_table

Answer 1

只需添加一个GROUP BY子句，而MySQL DATEDIFF()（后一个日期优先）不会像 day 那样使用单位参数，这可能会让您混淆不同的RDBMS像SQL Server这样的方法。

select MONTH(date_created) AS 'month',
       AVG(DATEDIFF(date_resolved, date_created)) AS 'avg_days', 
from my_table
group by MONTH(date_created);

Answer 2

您是否尝试转换为日期格式而不是使用datetime？

select AVG(DATEDIFF(day, convert(date,date_created,102),convert(date,date_removed,102)) )
from table

SQL - 获得GROUP BY个月的平均计数

2 个答案: