JPQL语法总结
| JPQL主要用于JPA查询数据，和SQL语句的语法大同小异；
最基本的查询： SELECT p FROM Player p
查询出所有的player,包括其子类，也可以写成这样 From Player as p
去除重复的元素 SELECT DISTINCT p FROM Player p WHERE p.position = ?1
关键字DISTINCT去 除了重复的元素，并且接受参数设置条件过滤
结合查询关联 SELECT DISTINCT p FROM Player p, IN(p.teams) t
查询所有有team的player 也可以写成如下：
SELECT DISTINCT p FROM Player p JOIN p.teams t
或者：
SELECT DISTINCT p FROM Player p WHERE p.team IS NOT EMPTY
关联关系的查询过滤 SELECT t FROM Team t JOIN t.league l WHERE l.sport = ’soccer’ OR l.sport =’football’ 查询所有league sports属性的team对象
SELECT DISTINCT p FROM Player p, IN (p.teams) t WHERE t.league.sport = :sport 其他的查询表达式
LIKE： SELECT p FROM Player p WHERE p.name LIKE ’Mich%’
IS NULL： SELECT t FROM Team t WHERE t.league IS NULL
IS EMPTY： SELECT p FROM Player p WHERE p.teams IS EMPTY 主要用于判断关系实体一对多集合
BETWEEN SELECT DISTINCT p FROM Player p WHERE p.salary BETWEEN :lowerSalary AND :higherSalary
等价于： p.salary >= :lowerSalary AND p.salary <= :higherSalary
在 判断日期范围的时候尤其有用；
复 合条件： SELECT DISTINCT p1 FROM Player p1, Player p2 WHERE p1.salary > p2.salary AND p2.name = :name 查找薪水比指定姓名的员工更高的 员工
IN： o.country IN (’UK’, ’US’, ’France’)
同时你也可以在In语句中设置参数： o.country IN (’UK’, ’US’, ’France’, :country)
子 查询： SELECT c FROM Customer c WHERE (SELECT COUNT(o) FROM c.orders o) > 10
EXISTS子查询： SELECT DISTINCT emp FROM Employee emp WHERE EXISTS ( SELECT spouseEmp FROM Employee spouseEmp WHERE spouseEmp = emp.spouse)
ALL和ANY配合=<>=>使用 SELECT emp FROM Employee emp WHERE emp.salary > ALL ( SELECT m.salary FROM Manager m WHERE m.department = emp.department)
其他函数：
算法函数：
返回参数：
1） 实体对象
SELECT t FROM Player p, IN (p.teams) t
2) Objecth或者Object[] SELECT c.name, c.country.name FROM customer c WHERE c.lastname = ’Coss’ AND c.firstname = ’Roxane’ 返回一个Object[] list,[0]为name，[1]为country name
Select语句的聚合函数：
如： SELECT COUNT(l.price) FROM Order o JOIN o.lineItems l JOIN o.customer c WHERE c.lastname = ’Incandenza’ AND c.firstname = ’Hal’
构造语句： SELECT NEW com.xyz.CustomerDetail(c.name, c.country.name) FROM customer c WHERE c.lastname = ’Coss’ AND c.firstname = ’Roxane’
能够利用查出的数据直接构造出对象
Order By： SELECT p.product_name FROM Order o, IN(o.lineItems) l JOIN o.customer c WHERE c.lastname = ’Faehmel’ AND c.firstname = ’Robert’ ORDER BY o.quantity
GROUP BY： SELECT c.country, COUNT(c) FROM Customer c GROUP BY c.country
Having：
SELECT c.status, AVG(o.totalPrice) FROM Order o JOIN o.customer c GROUP BY c.status HAVING c.status IN (1, 2, 3) |