在 pgadmin 中运行良好，但在 java 代码中不起作用

Question

with recursive
Ancestor(a,d) as (select parent as a, child as d from ParentOf
union
select Ancestor.a , ParentOf.child as d 
from Ancestor, ParentOf
where Ancestor.d = ParentOf.parent)

嗨，我在 pgadmin 中运行了上面的代码，它运行良好，所以我尝试以同样的方式将它移动到我的 java 代码中。 但在这里它被称为 SQL 语法中的错误。 这是什么原因？ 我也放了； 在 SQL 语句中，但发生了同样的错误。

stmt.executeUpdate("with recursive " +
                    "Ancestor(a,d) as (select parent as a, child as d from ParentOf " +
                    "union " +
                    "select Ancestor.a , ParentOf.child as d  " +
                    "from Ancestor, ParentOf " +
                    "where Ancestor.d = ParentOf.parent)");

下面是错误

Exception in thread "main" org.postgresql.util.PSQLException: error: syntax error, at the end of input
  Position: 185
    at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2553)
    at org.postgresql.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2285)
    at org.postgresql.core.v3.QueryExecutorImpl.execute(QueryExecutorImpl.java:323)
    at org.postgresql.jdbc.PgStatement.executeInternal(PgStatement.java:473)
    at org.postgresql.jdbc.PgStatement.execute(PgStatement.java:393)
    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:322)
    at org.postgresql.jdbc.PgStatement.executeCachedSql(PgStatement.java:308)
    at org.postgresql.jdbc.PgStatement.executeWithFlags(PgStatement.java:284)
    at org.postgresql.jdbc.PgStatement.executeUpdate(PgStatement.java:258)
    at SqlTest3.main(SqlTest3.java:44)

Answer 1

你有两个错误。 首先，要运行查询，您需要使用executeQuery() 。 其次，Java 中的 SQL 字符串不包含最终的SELECT语句，它只包含 CTE。

ResultSet rs = stmt.executeQuery(
         "with recursive "Ancestor(a,d) as (" + 
         "select parent as a, child as d from ParentOf " +
         "union " +
         "select Ancestor.a  ParentOf.child as d  " +
         "from Ancestor " +
         " join ParentOf on Ancestor.d = ParentOf.parent " + 
         ") "  + 
         "select * from ancestor"); // <<< this SELECT was missing

我还用“现代”（超过 25 年）显式 JOIN 运算符替换了 where 子句中古老而过时的隐式连接，这是目前推荐的编写连接的方法。