如何将sql查询转换为休眠查询

Question

我有 q sql 查询，我使用子查询和左连接获取数据。它在 sql server 上正常工作，但是当我在 hibernate 中使用 HQL 使用此查询时，它说意外令牌 (;

下面是我在 sql server 上运行良好的查询 -

SELECT IH.vendorName, IH.C, IHP.CP FROM (SELECT vendorName, count(*) as C 
FROM InvoiceHeader GROUP BY vendorName) IH LEFT JOIN (SELECT vendorName, 
count(*) AS CP FROM InvoiceHeader WHERE invoiceStatus='Processed' GROUP BY 
vendorName) IHP ON IHP.vendorName=IH.vendorName ORDER BY IH.C DESC

我正在尝试将我的 sql 查询转换为 HQL

Query q = sessionFactory.getCurrentSession().createQuery("SELECT 
IH.vendorName, IH.C, IHP.CP FROM (SELECT vendorName, count(*) as C FROM 
InvoiceHeader GROUP BY vendorName) IH LEFT JOIN (SELECT vendorName, count(*) 
AS CP FROM InvoiceHeader WHERE invoiceStatus='Processed' GROUP BY 
vendorName) IHP ON IHP.vendorName=IH.vendorName ORDER BY IH.C DESC"); 

但我收到此错误

org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: line 1:41: unexpected token: (
org.hibernate.hql.internal.ast.ErrorCounter reportError
ERROR: line 1:61: unexpected token: count

Answer 1

以下是部分操作方法。

首先，您的查询需要简化，因为联接根本没有效率。 MSSQL 不支持 FILTER，但Modern SQL 向我们展示了一个足够的替代方案。

SELECT vendorName, sum(case when invoiceStatus = 'Processed' then 1 end) as CP, count(*) as C FROM InvoiceHeader GROUP BY vendorName ORDER BY C DESC;

其次，如果事实证明无法将其转换为 HQL，您可以使用 createNativeQuery，但这是我的尝试：

SELECT I.vendorName, COUNT(I) as C, SUM(CASE WHEN I.invoiceStatus = 'Processed' THEN 1 END) AS CP FROM InvoiceHeader I GROUP BY I.vendorName ORDER BY C DESC

使用表别名很重要，这样它才能在查询中正确解析，即使它是唯一的表。