grails - Grails 多对多 - 查找所有不包含特定对象的对象

Question

我有以下域模型：

class Product {
    static hasMany = [ certificates : Certificate ]
}

class Certificate {
    static hasMany = [ products : Product ]
    static belongsTo = [ Product ]
}

如何找到所有不包含特定证书的产品？最好带有条件查询。

Answer 1

使用 Burt在此处建议的方法

您可以这样编写查询：

 def p = new Product(message:"A")
 p.addToCertificates (new Certificate(message:"1").save(flush:true) )
 p.addToCertificates (new Certificate(message:"2").save(flush:true) )
 p.addToCertificates (new Certificate(message:"3").save(flush:true) )
 p.save(flush:true)

 p = new Product(message:"B")
 p.addToCertificates (new Certificate(message:"1").save(flush:true) )
 p.addToCertificates (new Certificate(message:"2").save(flush:true) )
 p.save(flush:true)

 p = new Product(message:"C")
 p.addToCertificates (new Certificate(message:"1").save(flush:true) )
 p.addToCertificates (new Certificate(message:"2").save(flush:true) )
 p.save(flush:true) 


def cer= Certificate.findByMessage("3")
Product.executeQuery(
'select p from Product p where :certificate not in elements(p.certificates)',[certificate: cer])

输出：

结果：[B，C]

Answer 2

尝试这个：

Certificate certificate = Certificate.findTheSpecificOne()

def c = Product.createCriteria()
def results = c.list {
  createAlias("certificates", "c", CriteriaSpecification.LEFT_JOIN)
  not {'in'("c", certificate)}
}