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： CONCAT(String, String) String LENGTH(String) int LOCATE(String, String [, start]) int SUBSTRING(String, start, length) String TRIM([[LEADING|TRAILING|BOTH] char) FROM] (String) String LOWER(String) String UPPER(String) String 算法函数： Function Syntax Return Type ABS(number) int,float, ordouble MOD(int, int) int SQRT(double) double SIZE(Collection) int 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： AVG Double Returns the mean average of the fields. COUNT Long Returns the total number of results. MAX the type of the field Returns the highest value in the result set. MIN the type of the field Returns the lowest value in the result set. SUM Long(for integral fields)Double(for floating point fields)BigInteger(forBigIntegerfields)BigDecimal(forBigDecimalfields) Returns the sum of all the values in the result set. 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)