DATE_SUB()怎么使用
时间: 2023-05-18 20:05:30 浏览: 195
DATE_SUB()函数用于从日期中减去一定的时间间隔。它的语法如下:
```
DATE_SUB(date, INTERVAL expr unit)
```
其中,date是要减去时间间隔的日期,expr是时间间隔的数量,unit是时间间隔的单位。unit可以是以下值之一:
- MICROSECOND
- SECOND
- MINUTE
- HOUR
- DAY
- WEEK
- MONTH
- QUARTER
- YEAR
下面是一些使用DATE_SUB()函数的示例:
1. 从当前日期中减去1天:
```
SELECT DATE_SUB(NOW(), INTERVAL 1 DAY);
```
2. 从指定日期中减去2个月:
```
SELECT DATE_SUB('2021-01-01', INTERVAL 2 MONTH);
```
3. 从指定日期中减去3周:
```
SELECT DATE_SUB('2021-01-01', INTERVAL 3 WEEK);
```
4. 从指定日期中减去4小时:
```
SELECT DATE_SUB('2021-01-01 12:00:00', INTERVAL 4 HOUR);
```
注意:DATE_SUB()函数返回的是一个日期类型的值,可以直接用于比较或者作为其他函数的参数。
相关问题
SELECT DATE_FORMAT( dmtr.`day`,'%Y-%m-%d') as oneday, dmtr.column_num, dmtr.table_num FROM dap_metadata_table_record AS dmtr GROUP BY oneday HAVING oneday >= DATE_SUB(CURDATE(), INTERVAL 7 DAY) UNION ALL SELECT d.`day`, 0, 0 FROM ( SELECT DATE_SUB(CURDATE(), INTERVAL 7 DAY) AS day UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 6 DAY) UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 5 DAY) UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 4 DAY) UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 3 DAY) UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 2 DAY) UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 1 DAY) ) AS d LEFT JOIN dap_metadata_table_record AS dmtr1 ON d.`day` = dmtr1.`day` WHERE dmtr1.`day` IS NULL ORDER BY oneday DESC; 修改sql只查询七条
你可以将原来的查询语句中的 `HAVING` 子句改为 `WHERE` 子句,并添加一个条件限制只查询最近七天的记录,修改后的 SQL 查询语句如下:
```
SELECT DATE_FORMAT(dmtr.`day`, '%Y-%m-%d') AS oneday, dmtr.column_num, dmtr.table_num
FROM dap_metadata_table_record AS dmtr
WHERE dmtr.`day` >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)
GROUP BY oneday
UNION ALL
SELECT d.`day`, 0, 0
FROM (
SELECT DATE_SUB(CURDATE(), INTERVAL 7 DAY) AS day
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 6 DAY)
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 5 DAY)
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 4 DAY)
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 3 DAY)
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 2 DAY)
UNION ALL SELECT DATE_SUB(CURDATE(), INTERVAL 1 DAY)
) AS d
LEFT JOIN dap_metadata_table_record AS dmtr1 ON d.`day` = dmtr1.`day`
WHERE dmtr1.`day` IS NULL
ORDER BY oneday DESC
LIMIT 7;
```
以上 SQL 查询语句中,`WHERE dmtr.`day` >= DATE_SUB(CURDATE(), INTERVAL 7 DAY)` 子句限制只查询最近七天的记录,`LIMIT 7` 子句限制只查询七条记录。
date_sub(date_sub(curdate(),interval 1 day),interval 1 year
你的问题是如何将当前日期减去一天再减去一年?可以使用以下MySQL语句实现:
```
SELECT DATE_SUB(DATE_SUB(CURDATE(), INTERVAL 1 DAY), INTERVAL 1 YEAR);
```
这将返回当前日期减去一天再减去一年的结果。请注意,这是一个示例,具体的语法可能因您使用的数据库系统而有所不同。
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