MySQL tutorial proofreading set problem

This article mainly introduces you to the proofreading set problem in mysql. I hope it will be helpful to friends in need!

Recommended reference tutorial: "mysql tutorial"

Proofreading set problem

Proofreading set is actually a way of comparing data.

There are three types of proofreading sets, namely:

• _bin: binary, binary comparison, case-sensitive;

• _cs：case sensitive, case sensitive, case sensitive;

• _ci：case insensitive, case insensitive, not case sensitive.

View (all) proofreading sets–> Basic syntax: show collation;

##As shown above As shown, MySQL database supports more than one hundred collation sets.

Next, let’s take a look at the application of the proofing set, because the proofing set will only take effect when the data is compared. Here, we use two proofreading sets of

utf8_bin and _ci for comparison:

-- 创建两张使用不同校对集的表create table my_collate_bin(
    name char(MySQL tutorial proofreading set problem)
)charset utf8 collate utf8_bin;create table my_collate_ci(
    name char(MySQL tutorial proofreading set problem)
)charset utf8 collate utf8_general_ci;

As shown in the figure above, we created two tables, namely

my_collate_bin and my_collate_ci, and their proofing sets are _bin and _ci## respectively. #. Then, add data to these two tables respectively: <pre class="brush:php;toolbar:false;">-- 向表中添加数据insert into my_collate_bin values (&amp;#39;a&amp;#39;),(&amp;#39;A&amp;#39;),(&amp;#39;B&amp;#39;),(&amp;#39;b&amp;#39;);insert into my_collate_ci values (&amp;#39;a&amp;#39;),(&amp;#39;A&amp;#39;),(&amp;#39;B&amp;#39;),(&amp;#39;b&amp;#39;);</pre> Then view the data in the two tables respectively:

-- 查看表中的数据select * from my_collate_bin;select * from my_collate_ci;

Next, we will use the To sort by a certain field (both

my_collate_bin

and my_collate_ci have only one field), the basic syntax is: <pre class="brush:php;toolbar:false;">order by + 字段名 + [asc/desc];</pre>where,

asc

means ascending order, desc means descending order, and the default is ascending order. Execute the following SQL statement: <pre class="brush:php;toolbar:false;">-- 排序比较select * from my_collate_bin order by name;select * from my_collate_ci order by name;</pre>

As shown in the picture above, obviously the proofreading set is effective!

In addition, we need to pay special attention to the following:

The proofing set must be declared before there is no data. If the proofing set is modified after there is data, the modification will be invalid.

Warm reminder:

The content enclosed by the symbols [] represents optional options; the symbols represent the meaning of connection

The above is the detailed content of MySQL tutorial proofreading set problem. For more information, please follow other related articles on the PHP Chinese website!