Question

我的数据库中有这个结构和一些数据，结果我想要：

现在，我使用子查询，如下所示：

SELECT dem2.id, 
       (SELECT TOP 1 datetime 
        FROM   demand 
        WHERE  department = 'Logisitc' 
               AND action = 'Shipped' 
               AND comment = 'B' 
               AND id = dem2.id 
        ORDER  BY datetime DESC), 
       (SELECT actor 
        FROM   service_call_env 
        WHERE  id = dem2.id), 
       (SELECT TOP 1 datetime 
        FROM   demand 
        WHERE  department = 'Sale' 
               AND action = 'Email' 
               AND id = dem2.id 
        ORDER  BY datetime DESC), 
       ( Isnull((SELECT TOP 1 Isnull(Cast(demand.datetime AS VARCHAR(30)), NULL) 
         FROM 
         demand WHERE department = 'Update' AND id = dem2.id), NULL) 
         + Isnull((SELECT TOP 1 Isnull(demand.comment, NULL) FROM demand WHERE 
         department = 'Update' AND id = dem2.id), NULL) ), 
       (SELECT TOP 1 datetime 
        FROM   demand 
        WHERE  department = 'Admin' 
               AND comment IS NULL 
               AND id = dem2.id 
        ORDER  BY datetime DESC), 
       (SELECT TOP 1 dem1.datetime 
        FROM   demand 
        WHERE  department = 'Sale' 
               AND action = 'NewAddress' 
               AND id = dem2.id 
        ORDER  BY datetime DESC), 
       (SELECT TOP 1 search_name 
        FROM   demand dem1 
               INNER JOIN person 
                       ON person.person_id = dem1.USER 
        WHERE  dem1.department = 'Sale' 
               AND dem1.action = 'NewAddress' 
               AND dem1.id = dem2.id 
        ORDER  BY dem1.datetime DESC) 
FROM   demand dem1 
       INNER JOIN (SELECT id 
                   FROM   demand) AS dem2 
               ON dem1.id = dem2.id

INNER JOIN很奇怪，但我需要使用它，因为这个查询是一个更大的提取。

你能帮助我吗，因为我尝试了一些LEFT JOIN，但我的查询需要很长时间才能执行？

Answer 1

您可以创建一个包含所有列的临时表，并进行插入或更新以感受它们。这将使您的代码更清晰。

您需要检查表索引策略的另一点。检查表中有关在where子句上使用的列的索引，并且不要忘记在索引的include部分中包含投影列。

如何更好地加入我的查询

1 个答案: