Question

我有一个名为count的字段，其值为 10-3，现在我想通过在所有行中查找3/10并按此排序来排序在mysql中可以吗？

Answer 1

首先，您应该修复数据结构。在字段中存储两个不同的值只是糟糕的关系数据库设计。将字符串存储为数字也是不好的设计。

但是，有时我们会遇到其他人糟糕的设计决策。在MySQL中，在您的情况下这很容易：

>> # Starting with nothing.

>> git status
fatal: Not a git repository (or any of the parent directories): .git

>> git init
Initialized empty Git repository in C:/Users/q/Documents/GitHub/.git/

>> ls

>> git status
On branch master
Initial commit
nothing to commit (create/copy files and use "git add" to track)

>> echo "New file created." > t.txt

>> git status
On branch master
Initial commit
Untracked files:
  (use "git add <file>..." to include in what will be committed)
        t.txt
nothing added to commit but untracked files present (use "git add" to track)


>> git add .

>> git status
On branch master
Initial commit
Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
        new file:   t.txt


>> #open t.txt and add a second line of text to it

>> git status
On branch master
Initial commit
Changes to be committed:
  (use "git rm --cached <file>..." to unstage)
       new file:   t.txt
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)
        modified:   t.txt


>> git diff
diff --git a/t.txt b/t.txt
index e7a4f8a..fe91a49 100644
Binary files a/t.txt and b/t.txt differ

>> #How can I see the exact change?
>> #Something like: '''
>> #
>> # + This is the added line.
>> #
>> # ''' in the diff?


>> # I can take this even further by making the first commit, modifying, then staging the file 
                              # with `git add`, then editing again, and then run all three `git-diff`s 
                              # (git diff, git diff --cached, git diff HEAD) and none of them will specify any actual 
                              # changes in the files; Git still just lists the files that have discrepancies, without 
                              # listing any of the detials about /what/ is actually different.


>> git add .

>> git commit -m "Committed with the second line."
[master (root-commit) 14acc45] Committed with the second line.
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 t.txt

>> git diff

>> git log
commit 14acc455b16ba26cdea1661166b0ffc3fa089784
Author: q <q@gmail.com>
Date:   Sat Nov 7 04:29:20 2015 -0800
    Committed with the second line.

>> git diff HEAD

>> git diff HEAD^
fatal: ambiguous argument 'HEAD^': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'


>> #We change the file again to add a third line


>> git status
On branch master
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)
        modified:   t.txt
no changes added to commit (use "git add" and/or "git commit -a")


>> git diff
diff --git a/t.txt b/t.txt
index fe91a49..006c33a 100644
Binary files a/t.txt and b/t.txt differ


>> git diff HEAD
diff --git a/t.txt b/t.txt
index fe91a49..006c33a 100644
Binary files a/t.txt and b/t.txt differ


>> git add .

>> #Modify file again.

>> git status
On branch master
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)
        modified:   t.txt
Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git checkout -- <file>..." to discard changes in working directory)
        modified:   t.txt


>> git diff
diff --git a/t.txt b/t.txt
index 006c33a..57a6754 100644
Binary files a/t.txt and b/t.txt differ

>> git diff HEAD
diff --git a/t.txt b/t.txt
index fe91a49..57a6754 100644
Binary files a/t.txt and b/t.txt differ

>> git diff --cached
diff --git a/t.txt b/t.txt
index fe91a49..006c33a 100644
Binary files a/t.txt and b/t.txt differ

>>## But how do they differ?

它基本上将字符串分开并进行算术运算。

如何在Mysql中按一个formule排序

1 个答案: