SQLite and custom order by

问题:

I have a table with categories:

ID  Category
"1","Baking"   
"3","Family"   
"4","Entertaining"   
"5","Children"   
"6","Desserts"   

Now I would like to order the result of the select statement to

ID  Category
"4","Entertaining"   
"3","Family"  
"1","Baking"   
"5","Children"   
"6","Desserts"  

for example. In MySQL, you'd do it like this:

SELECT * FROM CATEGORIES ORDER BY FIELD (ID, 4,3,1,5,6);

How would you do it in SQLite though? I don't have an "order by" field.

回答1:

ORDER BY 
  CASE ID
    WHEN 4 THEN 0
    WHEN 3 THEN 1
    WHEN 1 THEN 2
    WHEN 5 THEN 3
    WHEN 6 THEN 4
  END

回答2:

I don't have an "order by" field

Why not?

If it is because the sort order is application sepcific then do the sort in the application rather than in the database.

If it is because the sort order is specific to just this one query then encode it in the query HOWEVER I strongly suggest you make this transparent to the calling application e.g. (Standard SQL syntax):

SELECT T2.ID, T2.Category, 
       T2.query_name_here_sort_order
  FROM (
        SELECT T1.ID, T1.Category, 
               CASE ID
                  WHEN 4 THEN 1
                  WHEN 3 THEN 2
                  WHEN 1 THEN 3
                  WHEN 5 THEN 4
                  WHEN 6 THEN 5
               END AS query_name_here_sort_order
          FROM CATEGORIES AS T1
       ) AS T2 (
                ID, Category, 
                query_name_here_sort_order
               )
 ORDER 
    BY query_name_here_sort_order;

If the sort order is used by multiple queries and/or applications then add it to a column in a table in the database then use that column in your query.

回答3:

A second way of doing it (the first one being with CASE WHEN ... THEN END as already stated in other answers) is:

ORDER BY ID=4 DESC,
         ID=3 DESC,
         ID=1 DESC,
         ID=5 DESC,
         ID=6 DESC