小编Ant*_*kin的帖子

有下表(Oracle 10g):

catalog (
  id NUMBER PRIMARY KEY,
  name VARCHAR2(255),
  owner NUMBER,
  root NUMBER REFERENCES catalog(id)
  ...
)
university (
  id NUMBER PRIMARY KEY,
  ...
)
securitygroup (
  id NUMBER PRIMARY KEY
  ...
)
catalog_securitygroup (
  catalog REFERENCES catalog(id),
  securitygroup REFERENCES securitygroup(id)
)
catalog_university (
  catalog REFERENCES catalog(id),
  university REFERENCES university(id)
)

目录:500 000行,catalog_university:500 000,catalog_securitygroup:1 500 000.

我需要从目录中选择任意50行,并为当前大学和当前安全组按名称排序指定的根.有一个查询:

SELECT ccc.* FROM (
  SELECT cc.*, ROWNUM AS n FROM (
      SELECT c.id, c.name, c.owner
        FROM catalog c, catalog_securitygroup cs, catalog_university cu …