Question

我需要从表中选择只有一行存在该ID的行。

示例表，有两列 ID优先和时间戳所以第一行是ID 1，时间戳01/01/2013

ID      Timestamp
1       01/01/2013
2       02/02/2013
3       04/02/2013
3       07/02/2013
4       20/03/2013

所以，对于这个表，我只想返回ID为1,2,4的记录，因为这些记录只有1行。

然后我需要只返回这些行，如果它们的时间戳超过一个月前。时间戳采用此格式2012-11-12-22.00.15.541231

有人可以帮忙吗？

Answer 1

这应该适合你：

SELECT *
FROM mytable
WHERE id NOT IN (
    SELECT id
    FROM mytable
    GROUP BY id
    HAVING COUNT(*) > 1
) AND time_created < current_timestamp - 1 month

Answer 2

您可以对此输出使用group by子句 -

修改

在datestamp列
上添加Condition
SELECT * FROM Your_Table_Name WHERE Id IN (SELECT Id FROM Your_Table_Name GROUP BY Id HAVING COUNT(*) = 1) AND time_created < current_timestamp - 1 month

Answer 3

这样的事情应该有效。

select id
from yourtable
where timestampfield <= current timestamp - 1 month
group by id
having count(*) = 1

减去1个月的部分来自here。

Answer 4

SQL Fiddle

MySQL 5.5.30架构设置：

CREATE TABLE Table1
    (`ID` int, `Timestamp` date)
;

INSERT INTO Table1
    (`ID`, `Timestamp`)
VALUES
    (1, '2013-01-01'),
    (2, '2013-02-02'),
    (3, '2013-04-02'),
    (3, '2013-07-02'),
    (4, '2013-03-20')
;

查询1 ：

select ID,Timestamp
from Table1
where DATEDIFF(curdate(),DATE_SUB(Timestamp,INTERVAL 1 MONTH))>=1
group by ID
having count(ID)=1

<强> Results ：

| ID |                       TIMESTAMP |
----------------------------------------
|  1 |  January, 01 2013 00:00:00+0000 |
|  2 | February, 02 2013 00:00:00+0000 |
|  4 |    March, 20 2013 00:00:00+0000 |

Answer 5

如果您只需要返回ID和时间戳，则可以避免使用子查询，如下所示：

SELECT ID, MAX(Timestamp) AS Timestamp
FROM atable
GROUP BY ID
HAVING COUNT(*) = 1
   AND MAX(Timestamp) < CURRENT TIMESTAMP - 1 MONTH
;

SQL坚持这个

5 个答案: