从单个表中进行双重排序选择

Question

我有一个表，其中id为主键，而描述为另一个字段。

我想首先选择id <= 4的记录，按描述排序，然后我想要所有其他记录（id> 4），按描述排序。无法到达那里！

Answer 1

select id, descr
from t
order by 
 case when id <= 4 then 0 else 1 end, 
 descr

Answer 2

select *, id<=4 as low from table order by low, description

Answer 3

您可能希望在id <= 4子句中使用ORDER BY表达式：

SELECT * FROM your_table ORDER BY id <= 4 DESC, description;

测试用例（使用MySQL）：

CREATE TABLE your_table (id int, description varchar(50));

INSERT INTO your_table VALUES (1, 'c');
INSERT INTO your_table VALUES (2, 'a');
INSERT INTO your_table VALUES (3, 'z');
INSERT INTO your_table VALUES (4, 'b');
INSERT INTO your_table VALUES (5, 'g');
INSERT INTO your_table VALUES (6, 'o');
INSERT INTO your_table VALUES (7, 'c');
INSERT INTO your_table VALUES (8, 'p');

结果：

+------+-------------+
| id   | description |
+------+-------------+
|    2 | a           |
|    4 | b           |
|    1 | c           |
|    3 | z           |
|    7 | c           |
|    5 | g           |
|    6 | o           |
|    8 | p           |
+------+-------------+
8 rows in set (0.00 sec)

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Answer 4

select id, description
from MyTable
order by case when id <= 4 then 0 else 1 end, description

Answer 5

您可以使用UNION

SELECT * FROM (SELECT * FROM table1 WHERE id <=4 ORDER by description)aaa
UNION
SELECT * FROM (SELECT * FROM table1 WHERE id >4 ORDER by description)bbb

OR

SELECT * FROM table1
ORDER BY
CASE WHEN id <=4 THEN 0
ELSE 1
END, description