删除重复行但保留 1 行（MySQL）

Question

我想删除重复的行，但条件如下

name  | tier |
—————————————|
geeni |  1   |
geeni |  1   |
geeni |  2   |
geeni |  3   |
geeni |  4   |
geeni |  4   |
geeni |  5   |

如何从 3 及以下的最小值中删除重复的行，但保留上面的其余行（4 和 5），即使它们也重复？

name  | tier |
—————————————|
geeni |  4   |
geeni |  4   |
geeni |  5   |

保留 4 的重复项而不删除它（仅 3,2 和 1）。如果可能的话请告诉我！到T

Answer 1

    -- Step 1: Identify the rows to keep (tiers 4 and 5).
WITH RowsToKeep AS (
    SELECT
        name,
        tier
    FROM
        YourTableName
    WHERE
        tier >= 4
),
-- Step 2: Identify the rows to delete based on conditions.
RowsToDelete AS (
    SELECT
        name,
        tier,
        ROW_NUMBER() OVER (PARTITION BY name, tier ORDER BY (SELECT NULL)) AS rn
    FROM
        YourTableName
    WHERE
        tier < 4
        AND EXISTS (
            SELECT 1
            FROM RowsToKeep
            WHERE RowsToKeep.name = YourTableName.name
              AND RowsToKeep.tier = YourTableName.tier
        )
)
-- Step 3: Delete the identified rows.
DELETE FROM YourTableName
WHERE EXISTS (
    SELECT 1
    FROM RowsToDelete
    WHERE RowsToDelete.name = YourTableName.name
      AND RowsToDelete.tier = YourTableName.tier
      AND RowsToDelete.rn > 1 -- Keeping one instance of each duplicate.
);