仅从 table 中获取每条 ID 记录的最大值

Question

我遇到了这样的 table，其中 id 重复了几次。

我只需要为每个 ID 获取最大 L1 值，因此查询的正确结果将是：

L1	ID	VALUE_VARCHAR
1	224754148	xDSL 1 - node_id atribut
2	224754147	adef_node_id_test_99
4	224754121	node_id_bijelnia_dvorovi
4	244378018	1

Table:

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (1, 224754121, 'node_id_bijelnia_dvorovi');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (1, 224754147, 'adef_node_id_test_99');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (1, 224754148, 'xDSL 1 - node_id atribut');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (1, 244378018, '1');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (2, 224754121, 'node_id_bijelnia_dvorovi');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (2, 224754147, 'adef_node_id_test_99');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (2, 244378018, '1');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (3, 224754121, 'node_id_bijelnia_dvorovi');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (3, 244378018, '1');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (4, 224754121, 'node_id_bijelnia_dvorovi');

INSERT INTO MY_TABLE(L1, ID, VALUE_VARCHAR) VALUES (4, 244378018, '1');

Answer 1

解析函数，如row_number，求助：

SQL> with temp as
  2    (select l1, id, value_varchar,
  3            row_number() over (partition by id order by l1 desc) rn
  4     from my_table
  5    )
  6  select l1, id, value_varchar
  7  from temp
  8  where rn = 1
  9  order by id;

        L1         ID VALUE_VARCHAR
---------- ---------- ------------------------------
         4  224754121 node_id_bijelnia_dvorovi
         2  224754147 adef_node_id_test_99
         1  224754148 xDSL 1 - node_id atribut
         4  244378018 1

SQL>

Answer 2

尝试在 window 函数上使用 max(l1)：

select distinct max(l1)over (partition by idn),idn,value_varchar
from my_table
order by max(l1)over (partition by idn)

样本：

create table my_table (l1 number, idn number, value_varchar varchar2(100));

INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (1, 224754121, 'node_id_bijelnia_dvorovi');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (1, 224754147, 'adef_node_id_test_99');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (1, 224754148, 'xDSL 1 - node_id atribut');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (1, 244378018, '1'); 
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (2, 224754121, 'node_id_bijelnia_dvorovi');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (2, 224754147, 'adef_node_id_test_99');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (2, 244378018, '1');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (3, 224754121, 'node_id_bijelnia_dvorovi');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (3, 244378018, '1');
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (4, 224754121, 'node_id_bijelnia_dvorovi'); 
INSERT INTO MY_TABLE(L1, IDn, VALUE_VARCHAR) VALUES (4, 244378018, '1');

结果：

1   224754148   xDSL 1 - node_id atribut
2   224754147   adef_node_id_test_99
4   224754121   node_id_bijelnia_dvorovi
4   244378018   1

Answer 3

WITH sorted_data AS
(
  select l1, id, value_varchar, rank() OVER (PARTITION BY id ORDER BY  l1 DESC) as r from my_table
)
SELECT * FROM sorted_data WHERE r = 1;

4   224754121   node_id_bijelnia_dvorovi    1
2   224754147   adef_node_id_test_99    1
1   224754148   xDSL 1 - node_id atribut    1
4   244378018   1   1

仅从 table 中获取每条 ID 记录的最大值

Get only max values from table for each ID record

sql

oracle

greatest-n-per-group