0 
UPDATE nas_backup
SET fiber_serviceability_class = '0', 
last_updated_ts = CURRENT_TIMESTAMP 
WHERE location_id IN ( 
SELECT location_id 
FROM ( 
WITH distinct_locs AS ( 
    SELECT location_id, boundary_type 
    FROM ( 
        SELECT location_id, boundary_type 
        FROM nc
        WHERE technology_type = 'Fibre' 
    ) 
    GROUP BY location_id, boundary_type 
    HAVING COUNT( * ) = 1
)
SELECT nas.location_id
FROM distinct_locs, nas_backup nas
WHERE distinct_locs.location_id = nas.location_id
AND distinct_locs.boundary_type = 'FSA'
GROUP BY nas.location_id
)
);

任何人都可以提出一种优化查询的方法。现在需要超过5分钟。

表 nc 有 1600 万条记录，表 nas_backup 有 200 万条记录。

4

2 回答 2

0

我在这里说的大部分事情无论如何都应该由一个好的优化器完成，所以这主要是为了更好的可读性。

您已应用于位置部分的所有过滤器，因此将其带到子查询以减少结果集：

SELECT location_id, boundary_type 
FROM nc 
WHERE technology_type = 'Fibre' AND nc.boundary_type='FSA'
GROUP BY location_id, boundary_type 
HAVING COUNT(*) = 1

接下来，使用 JOIN 语法而不是隐式 Join：

UPDATE nas fiber_serviceability_class = '0', last_updated_ts = CURRENT_TIMESTAMP 
FROM nas_backup nas
    JOIN (SELECT location_id, boundary_type 
            FROM nc 
            WHERE technology_type = 'Fibre' AND nc.boundary_type='FSA'
            GROUP BY location_id, boundary_type 
            HAVING COUNT(*) = 1) loc ON loc.location_id=nas.location_id

我不知道带有 HAVING 子句的子查询是否有特殊原因。在不知道您的结构和数据的情况下，这只是一个猜测，但也许您不需要。这是一个非常简单的查询，转换为“同时更新技术类型为光纤且边界类型为 FSA 的每个 nas_backup”。

UPDATE nas fiber_serviceability_class = '0', last_updated_ts = CURRENT_TIMESTAMP 
FROM nas_backup nas
    JOIN nc ON nas.location_id=nc.location_id
WHERE nc.technology_type='Fibre'
    AND nc.boundary_type='FSA'
于 2014-06-12T11:09:10.290 回答
0

EXISTS可以帮助你一点。试试看：

UPDATE nas_backup
SET fiber_serviceability_class = '0', 
last_updated_ts = CURRENT_TIMESTAMP 
-- Remove the IN condition and check only that at least one row exists
WHERE EXISTS ( 
SELECT location_id 
FROM ( 
    WITH distinct_locs AS ( 
        SELECT location_id, boundary_type 
        FROM ( 
            SELECT location_id, boundary_type 
            FROM nc
            WHERE technology_type = 'Fibre'
        ) 
        GROUP BY location_id, boundary_type 
        HAVING COUNT( * ) = 1
    )
    SELECT
        nas.location_id
    FROM
        distinct_locs
    WHERE
        distinct_locs.boundary_type = 'FSA'
        -- This is the new line
        AND distinct_locs.location_id = nas_backup.location_id
    GROUP BY
        nas.location_id
    )
);

但是，如果您与我们分享您的数据库结构和您的目标，会更容易提供帮助。

下次请与我们分享您正在使用的 DBMS 的供应商和版本。

于 2014-06-12T10:24:14.720 回答