类型安全
适用于 ✅ 开源版 ✅ 专业版 ✅ 企业版
由集合运算符组合的度数小于 22 的两个子查询需要具有相同的度数，并且在大多数数据库中也需要具有相同的类型。 jOOQ 3.0 引入了 Typesafe Record[N] 类型，有助于编译时检查这些约束
// Some sample SELECT statements
Select<Record2<Integer, String>> s1 = select(BOOK.ID, BOOK.TITLE).from(BOOK);
Select<Record1<Integer>> s2 = selectOne();
Select<Record2<Integer, Integer>> s3 = select(one(), zero());
Select<Record2<Integer, String>> s4 = select(one(), inline("abc"));
// Let's try to combine them:
s1.union(s2); // Doesn't compile because of a degree mismatch. Expected: Record2<...>, got: Record1<...>
s1.union(s3); // Doesn't compile because of a type mismatch. Expected: <Integer, String>, got: <Integer, Integer>
s1.union(s4); // OK. The two Record[N] types match
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