MySQL implements sorting according to custom (specified order)

mysql sort according to the specified order (custom sort)

• I. Implement specified sorting requirements in mysql
• Second, the solution
• • 1: Custom sorting implementation
  • • 01. case when transformation to achieve custom sorting;
    • 02: mysql sorting function filed implements custom sorting (recommended);
    • 03: The function locate implements custom sorting;
    • 04: The function lnstr implements custom sorting;
    • 05: Use the data dictionary to implement custom sorting;

I. Implement specified sorting requirements in mysql

Under normal circumstances, we use the order by field asc/desc directly for sorting; but if the data format of the field to be sorted cannot be directly implemented, or we need to specify the order and there is no rule, a simple order by fieldIt cannot be achieved;
As shown in the figure below;

We need to sort according to the order of Bank of China, China Construction Bank, and Industrial and Commercial Bank of China; directly using the order by field cannot get the order we want

Similarly, for types, we want to sort in the order of repurchase, buy, and sell, and a simple order by field cannot be implemented;

Second, the solution

1: Custom sorting implementation

01. case when conversion implements custom sorting;

Use case when to convert Bank of China, China Construction Bank, and Industrial and Commercial Bank of China into 1, 2, and 3, so that we can use order by to implement custom rearrangement of data.

02: mysql sorting function filed implements custom sorting (recommended);

The field() function in MySQL can be used to sort the query result set in SQL in a specified order.
field(str,str1,str2,str3…) The field str returns the result set of the query in the order of the strings str1, str2, str3….If the str field value in the table does not exist in the records in str1, str2, str3, put it at the top of the result set and return it.

03: The function locate implements custom sorting;

You can also use the locate function to achieve sorting;
locate(subStr,string): determine whether the string (string) contains another string (subStr), the function returns the position where subStr appears in the string;

04: The function lnstr implements custom sorting;

INSTR(STR,SUBSTR) Search for the specified character (SUBSTR) in a string (STR), and return the position where the specified character is found (INDEX);
It is roughly the same as the locate function, but the function has a parameterFirst, one after;

05: Use the data dictionary to implement custom sorting;

For some relatively fixed fields, data dictionary items can generally be created, which is not only convenient for returning to the front-end for pull-down, etc., but also convenient for the maintenance of later additions and modifications, and can also give the corresponding order in the data dictionary; mainlyIt is convenient for later adjustment and maintenance; it is only necessary to modify the sorting in the data dictionary;
First, it is necessary to establish the corresponding data dictionary items in the data dictionary table and maintain the order;

Secondly, you can directly store the corresponding data dictionary value when storing, and then associate the query and use the data dictionarySort in order; just;

If the order changes,Or to add a new type, you only need to maintain it in the data dictionary, no need to modify sql, and the scalability is better (if necessary, it can even be specially maintained for the configuration page of the data dictionary);

For record only, for future reference, if there is any error, please feel free

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