我有一个 SQL 查询，它显示来自数据库中不同表的信息。然后，此查询显示在 DataGrid 中，我在 DropDownList 中有一些选项可以在 DataGrid 中搜索某些值。问题是搜索没有显示 CollectName 或 DeliverName 的正确信息。 下拉列表的代码:

 private static readonly Dictionary<string, string> SearchFields = new Dictionary<string, string> {
            { "Customer", "c.Name" },
            { "Department", "jn.Department" },
            { "CollectName", "SELECT Name FROM job_address WHERE AddressType = 3 AND JobID = jn.ID" },
            { "DeliverName", "(SELECT Name FROM job_address WHERE AddressType = 2 AND JobID = jn.ID)" }
        };

在 SQL 查询中，CollectName 和 DeliverName 是内部选择语句，这就是导致此处问题的原因，因为对 Customer 和 Department 的搜索工作正常。 SQL查询:

SELECT  c.Name,
        COUNT(distinct jn.ID) as Jobs,
        sum(jn.OutTurn) as Outturn,
        SUM(jn.ActualWeight) as GrossWt,
        SUM(jn.CBM) as CBM,
        jn.Department,
        (SELECT Name FROM job_address WHERE AddressType =3 AND JobID = jn.ID) as CollectName,
        (SELECT Name FROM job_address WHERE AddressType =2 AND JobID = jn.ID) as DeliverName       
FROM customer c
LEFT JOIN job_address ja ON c.AccountCode = ja.Code AND c.Company_ID = ja.Company_ID
JOIN  AddressType jat ON ja.AddressType = jat.ID and jat.Description = 'Debtor'
LEFT JOIN job_new jn ON ja.JobID = jn.ID
WHERE c.Company_ID = ?compid
GROUP BY c.ID

我有一个搜索功能，它采用从 DropDownList 中选择的值和在文本框中输入的值:

 List<MySqlParameter> param = new List<MySqlParameter>{ new MySqlParameter("compid", CompanyID) };
            StringBuilder SQL = new StringBuilder(SearchSQL);
            if (SearchFieldKey != null && SearchFieldKey.Length > 0)
            {
                SQL.Append(" AND (");
                for (int i = 0; i < SearchFieldKey.Length; i++)
                {
                    if (SearchFields.ContainsKey(SearchFieldKey[i]))
                    {

                        SQL.Append(SearchFields[SearchFieldKey[i]] + " LIKE ?parameter" + i.ToString());
                        param.Add(new MySqlParameter("parameter" + i.ToString(), "%" + SearchTerms[i] + "%"));

                        if (i != SearchFieldKey.Length - 1)
                            SQL.Append(" OR ");
                    }
                    else
                        throw new Exception("Error: Attempted to search on invalid field. Check SearchFields Argument.");
                }
                SQL.Append(") ");
            }

例如，我搜索一个客户，SQL 查询将这一行添加到末尾:

WHERE c.Company_ID = ?compid AND (c.Name LIKE ?parameter0) 

当我搜索 CollectName 或 DeliverName 时，查询是这样的:

WHERE c.Company_ID = ?compid AND (SELECT Name FROM job_address WHERE AddressType = 3 AND JobID = jn.ID LIKE ?parameter0)

此 SQL 查询是否存在导致 CollectName 和 DeliverName 无法工作的问题？

最佳答案

括号不符，应该是

WHERE c.Company_ID = ?compid 
AND (SELECT Name FROM job_address WHERE AddressType = 3 AND JobID = jn.ID) LIKE ?parameter0

要解决这个问题，您可以在字典中嵌入语句:

{ "CollectName", "(SELECT Name FROM job_address WHERE AddressType = 3 AND JobID = jn.ID)" },

或者在构建 SQL 的方法中，自动嵌入子查询:

SQL.Append("(" + SearchFields[SearchFieldKey[i]] + ") LIKE ?parameter" + i.ToString());

完全更正:如果您使用的是 StringBuilder，则不应尝试将字符串连接在一起:

var param = new List<MySqlParameter> { new MySqlParameter("compid", CompanyID) };
StringBuilder SQL = new StringBuilder(SearchSQL);
if (SearchFieldKey != null && SearchFieldKey.Length > 0)
{
    SQL.Append(" AND (");
    for (int i = 0; i < SearchFieldKey.Length; i++)
    {
        if (SearchFields.ContainsKey(SearchFieldKey[i]))
        {
            SQL.Append("(");
            SQL.Append(SearchFields[SearchFieldKey[i]]);
            SQL.Append(") LIKE ?parameter");
            SQL.Append(i);
            param.Add(new MySqlParameter("parameter" + i.ToString(), "%" + SearchTerms[i] + "%"));

            if (i != SearchFieldKey.Length - 1)
                SQL.Append(" OR ");
        }
        else
            throw new Exception("Error: Attempted to search on invalid field. Check SearchFields Argument.");
    }
    SQL.Append(") ");
}

关于c# - 搜索时 SQL 查询出错，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31313068/