# 14.5\. select子句 `select` 子句選擇將哪些對象與屬性返 回到查詢結果集中. 考慮如下情況: ``` select mate from Cat as cat inner join cat.mate as mate ``` 該語句將選擇`mate`s of other `Cat`s。（其他貓的配偶） 實際上, 你可以更簡潔的用以下的查詢語句表達相同的含義: ``` select cat.mate from Cat cat ``` 查詢語句可以返回值為任何類型的屬性，包括返回類型為某種組件(Component)的屬性: ``` select cat.name from DomesticCat cat where cat.name like 'fri%' ``` ``` select cust.name.firstName from Customer as cust ``` 查詢語句可以返回多個對象和（或）屬性，存放在 `Object[]`隊列中, ``` select mother, offspr, mate.name from DomesticCat as mother inner join mother.mate as mate left outer join mother.kittens as offspr ``` 或存放在一個`List`對象中, ``` select new list(mother, offspr, mate.name) from DomesticCat as mother inner join mother.mate as mate left outer join mother.kittens as offspr ``` 也可能直接返回一個實際的類型安全的Java對象, ``` select new Family(mother, mate, offspr) from DomesticCat as mother join mother.mate as mate left join mother.kittens as offspr ``` 假設類`Family`有一個合適的構造函數. 你可以使用關鍵字`as`給“被選擇了的表達式”指派別名: ``` select max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n from Cat cat ``` 這種做法在與子句`select new map`一起使用時最有用: ``` select new map( max(bodyWeight) as max, min(bodyWeight) as min, count(*) as n ) from Cat cat ``` 該查詢返回了一個`Map`的對象，內容是別名與被選擇的值組成的名-值映射。