更新时间:2022-10-18 09:32:27
不要试图做这样的事情:
从[User] U中选择*,其中convert(varchar(10),U.DateCreated,120)='2014-02-07'
这是一个更好的方法:
从[用户] U $ b $中选择* b其中U.DateCreated> ='2014-02-07'和U.DateCreated dateadd(day,1,'2014-02-07')
请参阅: Sargable
EDIT +
有2个基本避免在where子句(或连接条件)中使用数据的功能的原因。
2014-02-07
进行比较)。改变标准以适应数据效率要高得多。 修改适合数据的条件是我使用 SARGABLE
谓词
不要在两者之间使用。
日期和时间范围的***做法是避免BETWEEN和
总是使用以下格式:WHERE col> ='20120101'AND col 类型和所有精度,无论时间部分是否为
适用。
http://sqlmag.com/t-sql/ t-sql-best-practices-part-2 (Itzik Ben-Gan)
Select * from [User] U
where U.DateCreated = '2014-02-07'
but in the database the user was created on 2014-02-07 12:30:47.220
and when I only put '2014-02-07'
It does not show any data
DON'T be tempted to do things like this:
Select * from [User] U where convert(varchar(10),U.DateCreated, 120) = '2014-02-07'
This is a better way:
Select * from [User] U
where U.DateCreated >= '2014-02-07' and U.DateCreated < dateadd(day,1,'2014-02-07')
see: Sargable
EDIT + There are 2 fundamental reasons for avoiding use of functions on data in the where clause (or in join conditions).
2014-02-07
. It is far more efficient to alter the criteria to suit the data instead. "Amending the criteria to suit the data" is my way of describing "use SARGABLE
predicates"
And do not use between either.
the best practice with date and time ranges is to avoid BETWEEN and to always use the form:
WHERE col >= '20120101' AND col < '20120201' This form works with all types and all precisions, regardless of whether the time part is applicable.
http://sqlmag.com/t-sql/t-sql-best-practices-part-2 (Itzik Ben-Gan)