Grails Gorm按天计算元素组，无需时间

我希望检索每天的用户配置文件注册列表。 域对象UserProfile存储日期creationDate属性。 我试过了

def results = UserProfile.executeQuery('select u.creationDate, count(u) from UserProfile as u group by u.creationDate')
println results

这显然不是我所需要的，因为数据（已经）存储在其中，并且有完整的时间

任何资源精明的解决方案都适合：预测、hql

---

Thnks

将日期分解为

天

、

月

和

年

，然后忽略

时间戳

这会给你你所需要的

def query = 
"""
select new map(day(u.creationDate) as day, 
               month(u.creationDate) as month, 
               year(u.creationDate) as year, 
               count(u) as count)
       from UserProfile as u
       group by day(u.creationDate), 
                month(u.creationDate), 
                year(u.creationDate)
"""

//If you do not worry about dates any more then this should be enough
def results = UserProfile.executeQuery( query )

//Or create date string which can be parsed later
def refinedresults = 
    results.collect { [ "$it.year-$it.month-$it.day" : it.count ] }

//Or parse it right here
def refinedresults = 
    results.collect {
        [ Date.parse( 'yyyy-MM-dd', "$it.year-$it.month-$it.day" ) : it.count ]
    }

您可以将映射定义为公式，以提取日期和时间的日期部分。确切的公式将根据您使用的数据库而有所不同，对于MySQL，您可以使用

Date creationDay // not sure exactly what type this needs to be, it may need
                 // to be java.sql.Date instead of java.util.Date

static mapping = {
  creationDay formula: 'DATE(creation_date)'
}

（公式使用DB列名而不是GORM属性名）。现在，您可以按

creationDay

分组，而不是按

creationDate

分组，它应该可以执行您需要的操作

def query = 
"""
select new map(day(u.creationDate) as day, 
               month(u.creationDate) as month, 
               year(u.creationDate) as year, 
               count(u) as count)
       from UserProfile as u
       group by day(u.creationDate), 
                month(u.creationDate), 
                year(u.creationDate)
"""

//If you do not worry about dates any more then this should be enough
def results = UserProfile.executeQuery( query )

//Or create date string which can be parsed later
def refinedresults = 
    results.collect { [ "$it.year-$it.month-$it.day" : it.count ] }

//Or parse it right here
def refinedresults = 
    results.collect {
        [ Date.parse( 'yyyy-MM-dd', "$it.year-$it.month-$it.day" ) : it.count ]
    }

---

或者，您可以使用另一个答案中建议的年、月和日的单独字段来代替“日期”，我认为这些函数在H2和MySQL中都是有效的。

我使用HQL cast函数：

def results = UserProfile.executeQuery("""
  select cast(u.creationDate as date), count(u) 
  from UserProfile as u 
  group by cast(u.creationDate as date)
""")

---

基础数据库必须支持ANSI CAST（…AS…）语法来工作，这是PostgreSQL、MySQL、Oracle、SQL Server以及许多其他DBMS

依赖于方言的原因，这是我不考虑这个选项的原因。你说得对。：）我在executequery:HibernateQueryException:中使用CAST（）函数时遇到此异常，无法解析CAST:DATE的请求类型