Columns通常用于select 查询列，如下所示，效果等同：
query.createQuery(Class, new Columns("a","name","value"))
query.createQuery(Class, new Column("a","name"), new Column("a","value"))
说明：
|
对象 |
描述 |
|
new Columns("a", "name", "value") |
a. name, a.value 创建查询时： SELECT a.name, a.value FROM ... |
|
new Columns("a") .names("name","value") .asNames("n","v"); |
创建查询时： SELECT a.name AS n, a.value AS v FROM ... |
