- having和where之间最大区别:having主要争对组,可与聚合函数连用having sun(factor>1000);where主要针对单行元素,无法与聚合函数连用;
- node里面常用的时间格式转换:moment(npm包),标准格式化示例:moment.format;
- SQL的常用时间转换格式:FROM_UNIXTIME(time,'%Y-%m-%d')
//常用的一些时间函数查询
//昨天
select * from table_name where TO_DAYS(NOW())-TO_DAYS(时间字段名)<=1
* from table_name where TO_DAYS(NOW())-TO_DAYS(时间字段名)<=1//7天
select * from table_name where DATE_SUB(CURDATE(),INTERVAL 7 DAYS)<= date(时间字段名)
* from table_name where DATE_SUB(CURDATE(),INTERVAL 7 DAYS)<= date(时间字段名)//近30天
select * from table_name where DATE_SUB(CURDATE(),INTERVAL 30 DAYS)<= date(时间字段名)
* from table_name where DATE_SUB(CURDATE(),INTERVAL 30 DAYS)<= date(时间字段名)//当月
select * from table_name where DATE_FORMAT(时间字段名,'%Y%m') = DATE_FORMAT(CURDATE(),'%Y%m')
* from table_name where DATE_FORMAT(时间字段名,'%Y%m') = DATE_FORMAT(CURDATE(),'%Y%m')//上一月
select * from table_name where PERIOD_OFF(date_format(now(),'%Y%m'),date_format(时间字段名,'%Y%m'))=1
* from table_name where PERIOD_OFF(date_format(now(),'%Y%m'),date_format(时间字段名,'%Y%m'))=1 - group by在某些时候可以去重,会将完全相同的数据进行排序,即distinct
SELECT *,SUM(money) as smoney FROM ngo_dog_log WHERE pid=11 GROUP BY smoney DESC
*,SUM(money) as smoney FROM ngo_dog_log WHERE pid=11 GROUP BY smoney DESC - IN+数据,数据内容是select语句则只允许有一个字段,Exists前面则无字段,以select字段和值作为判定
- 利用sql查询得到非原生新的数据字段尽量与原生数据做区分,如原生数据为money,新数据字段最好用smoney
- select选择的元素利用(case when **** then ***end )as new_strname
SELECT id,value,pay_value,(case when sales_on='1'
id,value,pay_value,(case when sales_on='1'then 100
then 100when sales_on='0'
when sales_on='0'then 80
then 80end
end)as discount,
as discount,from yh_products
from yh_productswhere type =2 and state =2
where type =2 and state =2order by id desc
order by id desc - 常用辅助函数:length, concat, substring, count, max, min,sum,floor/ceil
//统计【】出现的频次
select substring_index(left(title,INSTR(title,']')-1),']',-1) from 'xxx_table'
substring_index(left(title,INSTR(title,']')-1),']',-1) from 'xxx_table'select substring_index(substring_index(title,'[',-1),']',-1) from 'xxx_table'
substring_index(substring_index(title,'[',-1),']',-1) from 'xxx_table'
高频SQL使用知识点
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转载自blog.csdn.net/sinat_20744625/article/details/98482166
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