Criteria接口的Projections類主要用于幫助Criteria接口完成數(shù)據(jù)的分組查詢和統(tǒng)計(jì)功能:
List cats=session.createCriteria(Cat.class)
.setProjection(Projections.projectionList()
.add(Projections.rowCount())
.add(Projections.avg("weight"))
.add(Projections.max("weight"))
.add(Projections.min("weight"))
.add(Projections.groupProperty("color"))
).addOrder(Order.asc("color")).list();
示例代碼相當(dāng)于:
select color,count(*),avg(weight),max(weight),min(weight),min(weight) from cat group by color order by color asc;
posted on 2007-05-15 08:50
josson 閱讀(2937)
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