需要帮助改进 SQL DELETE 性能

Question

我有两个关系，Customer 和 Adress。首先，我没有修改数据库的权限（比如为客户和地址创建新的比率）。我需要的是，给定状态列表，删除具有与该状态相关的 Adress1 或 Adress2 的客户。我在下面做的事情很慢，所以任何帮助将不胜感激。

foreach (State state in listOfStates)
{
  query = 
   "DELETE FROM CUSTOMER
    WHERE EXISTS (
     SELECT * FROM ADRESS
     WHERE CUSTOMER.ADRESS1 = ADRESS.ID
     AND STATE = " + state + ")";
  cmd.CommandText = query;
  cmd.ExecuteNonQuery();

  query = 
   "DELETE FROM CUSTOMER
    WHERE EXISTS (
     SELECT * FROM ADRESS
     WHERE CUSTOMER.ADRESS2 = ADRESS.ID
     AND STATE = " + state + ")";
  cmd.CommandText = query;
  cmd.ExecuteNonQuery();
}

Customer
+----------+---------+---------+--+
|   Name   | Adress1 | Adress2 |  |
+----------+---------+---------+--+
| John Doe |       1 |       2 |  |
| Victor   |       3 |       4 |  |
| Renat    |       5 |       6 |  |
+----------+---------+---------+--+

Adress

+----+--------+------+------------+
| ID | Street | City |   State    |
+----+--------+------+------------+
|  1 | xxx    | xxx  | California |
|  2 | xxx    | xxx  | Florida    |
|  3 | xxx    | xxx  | California |
|  4 | xxx    | xxx  | Ohio       |
|  5 | xxx    | xxx  | Virginia   |
|  6 | xxx    | xxx  | Colorado   |
+----+--------+------+------------+

Answer 1

我建议您为各州建立一个 IN 子句。如果您的 listOfStates 是 List<string>，这将是：

string states = "'" + string.Join("','", listOfStates) + "'";

（这将导致类似 'Arizona','Kentucky','Tennessee' 的结果，即 comma-separated 字符串，所有状态都用单引号引起来。）

如果 listOfStates 不是 List<string>，则调整以上内容以满足您的 collection 类型，例如

string states = "'" + string.Join("','", listOfStates.Select(state => state.Name)) + "'";

然后运行所有状态的单个删除语句：

query = 
 "DELETE FROM customer
  WHERE EXISTS (
   SELECT * FROM adress
   WHERE adress.id IN (customer.adress1, customer.adress2)
   AND adress.state IN (" + states + "))";

cmd.CommandText = query;
cmd.ExecuteNonQuery();

Answer 2

根据我使用 Access 的经验，联接通常比 WHERE EXISTS 子句快得多。

这应该可以通过复合 JOIN 来实现。以下是航空代码，但应该可以使用。

Access 喜欢在重要的 JOIN 子句中使用大量括号。

SELECT c.*
FROM CUSTOMER c
  INNER JOIN ADRESS a
    ON ((c.ADRESS1 = a.ID OR c.ADRESS2 = a.ID)
        AND (a.STATE = <state>)
       )

如果上述方法有效，只需将 SELECT 替换为 DELETE。

您也可以结合 Thorsten 的建议：

AND (a.STATE IN ('state1', 'state2'))

需要帮助改进 SQL DELETE 性能

Need help improving SQL DELETE performance

c#

sql

database

ms-access

sql-delete