SQL CASE语句与编程语言中的条件语句(SQL CASE Statement Versus Conditional Statements In Programming Language)
我在工作中经历了一些旧的存储过程并且经常遇到
CASE MyColumn WHEN 'Y' THEN 'Yes' WHEN 'N' THEN 'No' ELSE 'Unknown' END如果这不是一个单词，而是一个颜色，那就更糟了。
CASE MyColumn WHEN 'Y' THEN 'style="background-color:pink"' ELSE '' END这样做的原因是旧的ASP 1页面，其中所有内容都必须内联，但由于它是如此庞大的系统，因此无法跟上更新所有页面的步伐。
任何人都可以提供任何有效的证据证明对条件语句使用SQL查询超过了其他语言（如C＃或Java）吗？ 这是速度的好习惯吗？ 是否应该返回普通值并且表示层决定应该做什么？
I'm going through some old stored procedures at work and constantly come across
CASE MyColumn WHEN 'Y' THEN 'Yes' WHEN 'N' THEN 'No' ELSE 'Unknown' ENDIt gets even worse when this is tied not to a word, but instead a colour.
CASE MyColumn WHEN 'Y' THEN 'style="background-color:pink"' ELSE '' ENDThe reason this was done was for older ASP 1 pages where everything had to be done inline, but as it's such a large system it's impossible to keep up with updating all the pages.
Can anyone give any valid evidence that using a SQL query for conditional statements surpasses that in other languages such as C# or Java? Is this good practice for speed? Should the plain value be returned and the presentation layer decide what should be done?
原文：https://stackoverflow.com/questions/487770
最满意答案
我在CentOS 6.3上遇到了同样的问题。 问题最终是EPEL yum repo中没有collectd-dbi rpm。 你必须从其他地方获得dbi插件。
检查您已安装的collectd版本
$ yum info collectd这就是结果对我而言
Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile Installed Packages Name : collectd Arch : x86_64 Version : 4.10.7 Release : 1.el6 Size : 1.3 M Repo : installed From repo : epel您可以尝试在网络上搜索某人建立的RPM，但在我的情况下，我找不到我的确切版本。 因此，我认为唯一的解决方案是从源代码编译collectd。 以下是我编译collectd并安装dbi插件的步骤
克隆collectd仓库并签出您已安装的版本
git clone https://github.com/collectd/collectd.git cd collectd/ git checkout collectd-4.10.7安装依赖项以编译collectd。 以下是我需要安装以进行编译的所有内容，但您可能需要安装更多内容。 注意，libdbi-devel是必需的。 如果没有安装，那么在运行configure脚本时，dbi插件将不会启用而不会被编译。
sudo yum install autoconf automake flex ppl cloog-ppl cpp libgomp mpfr glibc-devel glibc-headers kernel-headers gcc libtool libtool-ltdl libtool-ltdl-devel libgcrypt-devel libgpg-error-devel libdbi libdbi-devel bison byacc db4-cxx db4-devel gdbm-devel perl-ExtUtils-MakeMaker perl-ExtUtils-ParseXS perl-Test-Harness perl-devel运行以下命令并确保没有错误
./build.sh && ./configure && make假设编译没有问题，那么你应该编译dbi插件。 你可以在
src/.libs/dbi.so找到它检查是否已安装所有链接库
$ ldd src/.libs/dbi.so linux-vdso.so.1 => (0x00007fff109ff000) libdbi.so.0 => /usr/lib64/libdbi.so.0 (0x00007fca4a53c000) libdl.so.2 => /lib64/libdl.so.2 (0x00007fca4a338000) libc.so.6 => /lib64/libc.so.6 (0x00007fca49fa3000) libm.so.6 => /lib64/libm.so.6 (0x00007fca49d1f000) /lib64/ld-linux-x86-64.so.2 (0x00007fca4a95a000)如果看起来不错，可以将dbi.so共享对象安装到collectd lib目录，如下所示：
sudo install -o root -g root src/.libs/dbi.so /usr/lib64/collectd/您现在应该可以重新启动collectd并加载dbi库
$ sudo service collectd restart Stopping collectd: [ OK ] Starting collectd: [ OK ]希望有所帮助
I had the same issue on CentOS 6.3. The problem ended up being that there is no collectd-dbi rpm in the EPEL yum repo. You'll have to get the dbi plugin from elsewhere.
Check which version of collectd you have installed
$ yum info collectdThis is what the results were for me
Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile Installed Packages Name : collectd Arch : x86_64 Version : 4.10.7 Release : 1.el6 Size : 1.3 M Repo : installed From repo : epelYou can try searching around the web for an RPM that someone built, but in my case I couldn't find one for my exact version. Because of this, I think the only solution is to compile collectd from source. The following are the steps I took to compile collectd and get the dbi plugin installed
Clone the collectd repo and checkout the version that you already have installed
git clone https://github.com/collectd/collectd.git cd collectd/ git checkout collectd-4.10.7Install dependencies to compile collectd. Below is everything I needed to install for compiling this, but there might be more you need to install. Note, libdbi-devel is required. If it doesn't get installed, then when running configure script, the dbi plugin will not enabled and not compiled.
sudo yum install autoconf automake flex ppl cloog-ppl cpp libgomp mpfr glibc-devel glibc-headers kernel-headers gcc libtool libtool-ltdl libtool-ltdl-devel libgcrypt-devel libgpg-error-devel libdbi libdbi-devel bison byacc db4-cxx db4-devel gdbm-devel perl-ExtUtils-MakeMaker perl-ExtUtils-ParseXS perl-Test-Harness perl-develRun the following and make sure there are no errors
./build.sh && ./configure && makeAssuming there were no issues compiling, then you should have the dbi plugin compiled. You can find it in
src/.libs/dbi.soCheck that you have all the linked libraries installed
$ ldd src/.libs/dbi.so linux-vdso.so.1 => (0x00007fff109ff000) libdbi.so.0 => /usr/lib64/libdbi.so.0 (0x00007fca4a53c000) libdl.so.2 => /lib64/libdl.so.2 (0x00007fca4a338000) libc.so.6 => /lib64/libc.so.6 (0x00007fca49fa3000) libm.so.6 => /lib64/libm.so.6 (0x00007fca49d1f000) /lib64/ld-linux-x86-64.so.2 (0x00007fca4a95a000)If that looks good, you can install the dbi.so shared object to the collectd lib directory like so:
sudo install -o root -g root src/.libs/dbi.so /usr/lib64/collectd/You should now be able to restart collectd and have the dbi library loaded
$ sudo service collectd restart Stopping collectd: [ OK ] Starting collectd: [ OK ]Hope that helps
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