为什么 JPQL 表达式不能导航到作为集合的关系字段之外？
Why JPQL expressions cannot navigate beyond relationship fields that are collections?
Excerpt from Java EE 7 tutorial:
SELECT DISTINCT p FROM Player p, IN (p.teams) AS t WHERE t.city = :city
Expressions cannot navigate beyond (or further qualify) relationship
fields that are collections. In the syntax of an expression, a
collection-valued field is a terminal symbol. Because the teams field
is a collection, the WHERE clause cannot specify p.teams.city (an
illegal expression).
为什么表达式不能导航到作为集合的关系字段之外？
我没有设计语言，我当然可以错过更重要的原因，但恕我直言，这没有多大意义：p.teams.city 读作 "the city property of the teams property of p"。但是 teams 是一个集合。并且集合没有任何 city 属性.
这至少是记住这不是有效 JPQL 的好方法。
Excerpt from Java EE 7 tutorial:
SELECT DISTINCT p FROM Player p, IN (p.teams) AS t WHERE t.city = :city
Expressions cannot navigate beyond (or further qualify) relationship fields that are collections. In the syntax of an expression, a collection-valued field is a terminal symbol. Because the teams field is a collection, the WHERE clause cannot specify p.teams.city (an illegal expression).
为什么表达式不能导航到作为集合的关系字段之外？
我没有设计语言，我当然可以错过更重要的原因，但恕我直言，这没有多大意义：p.teams.city 读作 "the city property of the teams property of p"。但是 teams 是一个集合。并且集合没有任何 city 属性.
这至少是记住这不是有效 JPQL 的好方法。