Question

data_table信息

idx | type | value
 1  |   1  |  1
 2  |   2  |  2
 3  |   3  |  3
 4  |   4  |  4

查询

SELECT * FROM data_table WHERE idx IN (1, 1, 2, 1, 1, 3, 4, 4, 1);

我收到了当前的结果：

idx | type | value
 1  |   1  |  1
 2  |   2  |  2
 3  |   3  |  3
 4  |   4  |  4

但我打算收到以下结果：

idx | type | value
 1  |   1  |  1
 1  |   1  |  1
 2  |   2  |  2
 1  |   1  |  1
 1  |   1  |  1
 3  |   3  |  3
 4  |   4  |  4
 4  |   4  |  4
 1  |   1  |  1

如何更改查询以获得所需结果？

Answer 1

我害怕你应该用union all写一些丑陋的sql：

select * from data_table where idx = 1
union all 
select * from data_table where idx = 1
union all
select * from data_table where idx = 2
union all 
select * from data_table where idx = 1
union all
select * from data_table where idx = 1
union all
select * from data_table where idx = 3
union all
select * from data_table where idx = 4
union all
select * from data_table where idx = 4
union all
select * from data_table where idx = 1

或类似的东西：

select data_table.*
from (
    select 1 idx
    union all select 1
    union all select 1
    union all select 2
    union all select 1
    union all select 1
    union all select 3
    union all select 4
    union all select 4
    union all select 1
) t
left join data_table
on t.idx = data_table.idx

注意： 第二种方式会让您获得不同的订单，并受到@Willem Van Onsem

的启发

Answer 2

解决此问题的一种潜在方法是动态创建表格，然后执行JOIN：

CREATE TEMPORARY TABLE ids (id INT NOT NULL);
INSERT INTO ids VALUES (1), (1), (2), (1), (1), (3), (4), (4), (1);

SELECT data_table.* FROM
FROM ids JOIN data_table ON data_table.idx = ids.id;

DROP ids;

Answer 3

如果您需要获取订购的行，您将硬编码的内容，那么您可以模拟其他列（在这种情况下为ord），然后在ORDER BY子句中使用此列：

 SELECT data_table.* FROM data_table
 inner join (
      select 1 as idx, 1 as ord
      union all
      select 1 as idx, 2 as ord
      union all
      select 2 as idx, 3 as ord
      union all
      select 1 as idx, 4 as ord
      union all
      select 1 as idx, 5 as ord
      union all
      select 3 as idx, 6 as ord
      union all
      select 4 as idx, 7 as ord
      union all
      select 4 as idx, 8 as ord
      union all
      select 1 as idx, 9 as ord
) your_list
on
data_table.idx = your_list.idx
order by your_list.ord

我想从MySQL中的多行中选择相同的值

3 个答案: