MySQL's little-known sorting method

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##Free learning recommendation: mysql video tutorial

ORDER BY field name ascending/descending order, I believe friends who come in know this sorting statement, but when encountering some special sorting, using field names alone cannot meet the needs. Here is what you need Introducing several sorting methods I have encountered:

1. Preparation work

For better demonstration and understanding, first prepare a student table, add numbers, Insert several pieces of data into the three fields of name and grades, as shown in the figure:

2. Conditional sorting

Requirement 1: Grades from high to Sorting by low

can be done by the aunties selling vegetables on the street. You can easily use

ORDER BY examScore DESC (as shown on the left below).

Requirement 2: The scores are sorted from high to low, and those who have not entered the scores are ranked first

Customer experience is the most important. In order to facilitate the second entry of scores, this requirement is purely normal. To achieve this sorting, the above statement cannot be implemented, so you need to use conditional sorting. First determine if the score is empty and assign a maximum value, and then sort, such as

ORDER BY IF(examScore IS NULL,101,examScore ) DESC can also be easily implemented (as shown on the right below).

RequirementsRequirements oneRequirements two StatementORDER BY examScore DESCORDER BY IF(examScore IS NULL,101,examScore) DESCEffect

3. Custom sorting

Customers are like God, and it is not uncommon for them to have fancy demands. For example, students are required to be ranked first, and other students are required to be ranked first according to their grades. Sort from high to low. In this case, you need to use custom sorting. MySQL's own FIELD function (returns the index of the corresponding string) can help you achieve this.

Statement 1:

ORDER BY FIELD(studentName,'Zhang San','Li Si') ASC, examScore DESC;

The above statement results are We have arranged Zhang San and Li Si at the end (as shown on the left below). It is logical that we should arrange Zhang San and Li Si at the front and sort them in descending order.

Statement 2:

ORDER BY FIELD(studentName,'李思','张三') DESC, examScore DESC;

The result is exactly what you want (as follows) right picture).

StatementStatement oneStatement two EffectLater I found that the FIND_IN_SET function can also be implemented, and tested using 1 million pieces of data. FIND_IN_SET performs better.

ORDER BY FIND_IN_SET(studentName,'李思,张三') DESC, examScore DESC;

##4. Sort by the first letter of Chinese pinyin

Some friends are surprised that sorting Chinese characters directly uses the ordinary

ORDER BY field ASC

and it is done easily. Why is it so little known? In fact, when users create table fields using the GBK character set, they can directly use the ORDER BY field ASC
to solve the problem. Some users use the utf8 character set to prevent garbled characters, and simple sorting statements are useless ( As shown in the left picture below), it is OK to convert the field to GBK when sorting (as shown in the right picture below).

StatementEffect##5. Guess you Like

ORDER BY studentName ASC	ORDER BY CONVERT(studentName USING GBK) ASC

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