MySQL查詢有了選擇具有不同與限制條件

Question

目前，我有一個下表，我想提取ID為帶有Estimate_date的記錄，這些記錄被分配給update_index值的最小值，如果該值為null，我想去分配給下一個update_index的值，

例如，用於記錄

• id = 73，我想獲取值2017-06-13 00:00:00
• id = 75，我想獲取值2017-01-01 00:00:00
• id = 76，我想獲取值2018-06-01 00:00:00

輸入表

+----+--------------+---------------------+
| id | update_index |    estimated_date   |
+----+--------------+---------------------+
| 73 |       1      | 2017-06-13 00:00:00 |
+----+--------------+---------------------+
| 73 |       2      | 2017-01-13 00:00:00 |
+----+--------------+---------------------+
| 73 |       3      | 2017-05-13 00:00:00 |
+----+--------------+---------------------+
| 73 |       4      |         NULL        |
+----+--------------+---------------------+
| 75 |       1      | 2017-01-01 00:00:00 |
+----+--------------+---------------------+
| 75 |       2      |         NULL        |
+----+--------------+---------------------+
| 75 |       3      | 2019-01-01 00:00:00 |
+----+--------------+---------------------+
| 76 |       1      |         NULL        |
+----+--------------+---------------------+
| 76 |       2      | 2018-06-01 00:00:00 |
+----+--------------+---------------------+

輸出表

+----+--------------+---------------------+
| id | update_index |    estimated_date   |
+----+--------------+---------------------+
| 73 |       1      | 2017-06-13 00:00:00 |
+----+--------------+---------------------+
| 75 |       1      | 2017-01-01 00:00:00 |
+----+--------------+---------------------+
| 76 |       2      | 2018-06-01 00:00:00 |
+----+--------------+---------------------+

我嘗試了以下值，但始終只能得到一個記錄，您能幫我嗎？

SELECT  id,update_index,estimated_date
FROM tablename where estimated_date = (
       SELECT DISTINCT estimated_date
       FROM tablename
        where estimated_date is not null
       ORDER BY id, udpate_index ASC
       LIMIT 1);
 `

Answer 1

我將使用相關的子查詢：

select t.*
from tablename t
where t.update_index = (select t2.update_index
                        from tablename t2
                        where t2.id = t.id and t2.estimated_date is not null
                        order by t2.update_index asc
                        limit 1
                       );

Answer 2

請嘗試這個。

    select t2.*
    from
    (select id, min(update_index) updated_index 
    from input_table 
    where estimated_date is not null
    group by 1 )t1
    left join input_table t2
    on t1.id = t2.id
    and t1.update_index = t2.update_index

Answer 3

您不能嘗試這樣：

從表名t選擇t.id，t.update_index，t.estimated_date，其中t.update_index =（從表名t1選擇MIN（update_index），其中t1.id = t.id並且t1.estimated_date不為空）按t.id分組

Answer 4

使用帶有LIMIT子句的子查詢：

select t.*
from table t
where t.update_index = (select t2.update_index
                        from table t2
                        where t2.id = t.id and t2.estimated_date is not null
                        order by t2.estimated_date desc
                        limit 1
                       );

但是，您的樣本數據進一步提示了我：

select t.*
from table t
where t.estimated_date = (select max(t2.estimated_date)
                          from table t2
                          where t2.id = t.id and t2.estimated_date is not null
                         );

如果您與estimated_date有聯系，則可以采用第一種方法。