Question

关于如何在C＃中编写长SQL查询的这个question，解决方案建议将一个长的SQL查询写成：

string query = @"
    SELECT
        c.CUSTOMER_ID,
        COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME
        ct.NAME as CUSTOMER_TYPE
    FROM
        CT_CUSTOMER_TYPE AS ct INNER JOIN CUSTOMER AS c
            ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID
    ";

这让我对另一个相关问题感到好奇。我能以某种方式使用替代吗？也就是说，如果说表名更改但查询保持不变，我将如何管理？我是否必须回归使用另一种使用字符串连接构建字符串的方法，还是有更优雅的方法？

Answer 1

为什么不使用string.Format？在您给出的具体示例中，您可以执行类似

的操作

string query = @"
SELECT
    c.CUSTOMER_ID,
    COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME
    ct.NAME as CUSTOMER_TYPE
FROM
    {0} AS ct INNER JOIN {1} AS c
        ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID
";

并调用

string real_query = string.Format(query, tblName1, tblName2);

Answer 2

是的，您可以使用String.Format方法。

string custtype = "CT_CUSTOMER_TYPE";
string cust = "CUSTOMER"; 
string query = @"
SELECT
    c.CUSTOMER_ID,
    COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME
    ct.NAME as CUSTOMER_TYPE
FROM
    {0} AS ct INNER JOIN {1} AS c
        ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID
"; 

string endQuery = String.Format(query, custtype, cust);

String.Format方法将使用字符串后面的参数顺序替换{x}标识的参数，因此{0}将替换为custtype的值，而{1}将替换为cust。

Answer 3

如果您还没有使用LINQ to SQL，可以考虑使用它。

回答实际问题，如果您正在创建查询，可以像其他人提到的那样使用string.Format。如果您想修改现有字符串，请按照here所述使用string.Replace或Regex.Replace。那就是：

string query = @"
    SELECT
        c.CUSTOMER_ID,
        COALESCE (c.FIRST_NAME, ''_ + ' ' + COALESCE (c.LAST_NAME, '') AS FULL_NAME
        ct.NAME as CUSTOMER_TYPE
    FROM
        CT_CUSTOMER_TYPE AS ct INNER JOIN CUSTOMER AS c
            ON ct.CUSTOMER_TYPE_ID = c.CUSTOMER_TYPE_ID
    ";
query.Replace("CT_CUSTOMER_TYPE", "NEW_TABLE_NAME");

在逐字字符串文字中替换？

3 个答案: