如何优化或删除以下查询中的冗余

Question

我有 4 个表

Table1 (employee)
id          name
--------------------
1           a
2           b

Table2 (appointment)
id    table1id    table3id    table4id   sdate    edate     typeid
-----------------------------------------------------------------------------------
1       1              1          1      1/1/09    NULL       100
2       2              2          1      1/1/09    NULL       101


Table3 (title)
id      name
---------------
1       worker1
2       worker2
3       Assistant
4       Manager

Table4 (Department names)
id      name
-------------------
1       Logistics
2       ABC
3       XYZ

Type
id       name
----------------
100      w (primary)
101      e (secondary)
102      r (other-primary)
103      t (.....)
104      y (....)

为了避免重复，我正在编写查询，因为

Select id, name, title, dept
FROM table1 a
INNER JOIN table2 b ON a.id = b.table1id
INNER JOIN table3 c ON b.table3id = c.id
INNER JOIN table4 d ON d.id = b.table4id
WHERE typeid =
        (
           SELECT min(type_id) /* i want primary type appointments */
           FROM table2
           WHERE sdate < getdate() and (edate > getdate() or edate IS NULL)
           AND sdate = (select max(sdate) from table2 where table1id = a.id)
           AND typeid in (100, 102)
        )
AND b.sdate < getdate() and (b.edate > getdate() or b.edate IS NULL)
AND b.sdate = (select max(sdate) from table2 where table1id = a.id)

/* last two i have to repeat again to remove dupes */

有没有一种方法可以减少使用相同条件两次并仅指定一次或任何其他更好的方法来查询它？ AND 输入 (100, 102)

Answer 1

在连接中使用子查询来获取所需的数字，这样的事情会是一种改进吗？

Select id, name, title, dept
FROM table1 a
INNER JOIN table2 b ON a.id = b.table1id
INNER JOIN table3 c ON b.table3id = c.id
INNER JOIN table4 d ON d.id = b.table4id
INNER JOIN (select max(sdate) from table2 group by table1id) new1 ON new1.table1id = a.id
WHERE typeid =
    (
       SELECT min(type_id) /* i want primary type appointments */
       FROM table2
       WHERE sdate < getdate() and (edate > getdate() or edate IS NULL)
       AND sdate = (select max(sdate) from table2 where table1id = a.id)
       AND typeid in (100, 102)
    )
AND b.sdate < getdate() and (b.edate > getdate() or b.edate IS NULL)
AND b.sdate = new1.sdate

您也可以尝试查看 GROUP BY 的 HAVING 子句。我认为你可以做类似的事情：

Select id, name, title, dept
FROM table1 a
INNER JOIN table2 b ON a.id = b.table1id
INNER JOIN table3 c ON b.table3id = c.id
INNER JOIN table4 d ON d.id = b.table4id
WHERE b.sdate < getdate() and (b.edate > getdate() or b.edate IS NULL)
AND typeid in (100, 102)
GROUP BY id, name, title, dept
HAVING b.sdate = max(sdate)
  AND typeid = min(type_id)

但是上面的代码可能会拉出整个列表的最小值和最大值，而不是每个a.id。我忘记是否可以使用 max 中的分区来指定 max 的范围，或者我是否正在考虑 Oracle。如果没有，您始终可以使用子查询来获取每个 a.id 的最佳条目。

Answer 2

我使用了相同的查询，它运行得很快，我没有找到任何其他方法来优化它