Question

表格 - col_pk，col1，col2，col3，col4，col_date_updated

此表包含一些行，其中col2和col3的列值重复。我想保留col_date_updated的那些行是最新的（最大）。

例如：

col_pk, col1, col2,  col3, col4,   col_date_updated
1,      A,    hello, now,  200.00, 2017-12-12 15:09:44.437546
2,      B,    hello, now,  490.00, 2017-12-12 15:09:42.437065
3,      C,    hi,    now,  300.00, 2017-12-12 15:09:41.436617
4,      D,    hello, now,  250.00, 2017-12-12 15:09:45.436617
5,      E,    hi,    now,  250.00, 2017-12-12 10:09:41.436617

预期结果：

col_pk, col1, col2,  col3, col4,   col_date_updated
3,      C,    hi,    now,  300.00, 2017-12-12 15:09:41.436617
4,      D,    hello, now,  250.00, 2017-12-12 15:09:45.436617

Answer 1

检查一下。

SELECT DISTINCT ON (col2, col3) t.*
FROM table t
ORDER BY col_date_updated DESC

在col2和col3上应用distinct，因为你希望它们是唯一的，并通过desc保持最新订单

Answer 2

如果您只是想选择来获得预期的输出，那么ROW_NUMBER会派上用场：

WITH cte AS (
    SELECT *, ROW_NUMBER() OVER (PARTITION BY col2, col3
        ORDER BY col_date_updated DESC) rn
    FROM yourTable
)
SELECT col_pk, col1, col2,  col3, col4, col_date_updated
FROM cte
WHERE rn = 1;

如果您想要删除其他记录，那么我们也可以重复使用CTE：

DELETE FROM yourTable WHERE col_pk IN (SELECT col_pk FROM cte WHERE rn > 1);

Answer 3

你可以尝试这样的事情。

SELECT t.*
  FROM yourtable t
 WHERE col_date_updated IN (SELECT MAX (col_date_updated)
                    FROM yourtable i
                   WHERE t.col2 = i.col2 AND t.col3 = i.col3);

所以，如果你想删除其他记录，你可以使用它。

DELETE 
  FROM yourtable t
 WHERE col_date_updated NOT IN (SELECT MAX (col_date_updated)
                    FROM yourtable i
                   WHERE t.col2 = i.col2 AND t.col3 = i.col3);

DEMO

Answer 4

如果要抑制除{col2，col3}之外的所有行（

）以外的所有行：

SELECT *
FROM thetable zt
WHERE NOT EXISTS (
        -- If a record exists with the same col2,col3,
        -- but a more recent date than zt.col_date_updated
        -- then zt.* cannot be the most recent one
        SELECT *
        FROM thetable nx
        WHERE nx.col2 = zt.col2 -- same value
        AND nx.col3 = zt.col3   -- same value
        AND nx.col_date_updated > zt.col_date_updated -- more recent
        );

如果您想要删除除{col2，col3}相同的最新行以外的所有行：

DELETE
FROM thetable zt
WHERE EXISTS (
        -- If a record exists with the same col2,col3,
        -- but a more recent date than zt.t.col_date_updated
        -- then zt.* cannot be the most recent one
        -- and we can delete zt.
        SELECT *
        FROM thetable nx
        WHERE nx.col2 = zt.col2 -- same value
        AND nx.col3 = zt.col3   -- same value
        AND nx.col_date_updated > zt.col_date_updated -- more recent
        );

Answer 5

这是最快的方式：

SELECT * FROM tablename WHERE col_pk IN 
       (SELECT col_pk FROM 
               (SELECT col_pk, ROW_NUMBER() OVER (partition BY col2, col3 ORDER BY col_date_updated) AS rnum
        FROM tablename) t
 WHERE t.rnum > 1);

如果你想删除：

DELETE FROM tablename WHERE col_pk IN 
       (SELECT col_pk FROM 
               (SELECT col_pk, ROW_NUMBER() OVER (partition BY col2, col3 ORDER BY col_date_updated) AS rnum
        FROM tablename DESC) t
 WHERE t.rnum > 1);

Pgsql删除一些列（不是全部）重复的行

5 个答案: