带有日期分隔符的 C# 和 MS Access SQL

Question

我遇到了这个查询的错误

"SELECT COUNT(*) AS x FROM accounts_info ";
        query += "INNER JOIN customers_info ON accounts_info.cust_code = customers_info.cust_code ";
        query += "WHERE accounts_info.date_due >= #@a# AND accounts_info.is_paid = 0";

OleDbCommand cmd = new OleDbCommand(query, con);
String aaa = DateTime.Now.ToString("MM/dd/yyyy");
cmd.Parameters.AddWithValue("@a", aaa);

一个错误告诉我：附加信息：查询表达式中的日期语法错误 'accounts_info.date_due >= #@a# AND accounts_info.is_paid = 0'。

我可以在日期分隔符 #1/13/2021# 中插入参数，例如 #@param@# 吗？

Answer 1

两件事

• 删除#
• 将参数值设为日期而不是字符串

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"SELECT COUNT(*) AS x FROM accounts_info ";
    query += "INNER JOIN customers_info ON accounts_info.cust_code = customers_info.cust_code ";
    query += "WHERE accounts_info.date_due >= @a AND accounts_info.is_paid = 0";

OleDbCommand cmd = new OleDbCommand(query, con);
cmd.Parameters.AddWithValue("@a", DateTime.Now.Date); //.Date will remove time portion from date

旁注..

OLEDB 不做命名参数。您可以将它们与名称一起放入，但您给出的名称无关紧要，重要的是顺序。参数集合必须包含相同数量的参数，并且与它们在 SQL 中出现的顺序相同。出于这个原因，为了避免误以为参数名称可以在查询中多次重复使用，有些人使用 ?参数占位符的标记

"SELECT COUNT(*) AS x FROM accounts_info ";
    query += "INNER JOIN customers_info ON accounts_info.cust_code = customers_info.cust_code ";
    query += "WHERE accounts_info.date_due >= ? AND accounts_info.is_paid = 0";

OleDbCommand cmd = new OleDbCommand(query, con);
cmd.Parameters.AddWithValue("p1", DateTime.Now.Date);

Answer 2

您的查询给出了下面的查询。

SELECT COUNT(*) AS x FROM accounts_info
INNER JOIN customers_info ON accounts_info.cust_code = customers_info.cust_code
WHERE accounts_info.date_due >= #@a# AND accounts_info.is_paid = 0

所以请从查询中删除#。

另外请创建一个存储过程并传递参数，而不是在代码中编写查询。