你的代码错误System.Data.SQLite.SQLiteException:“SQL logic error no such function: CONCAT”

抱歉，我之前给出的代码在使用 SQLite 数据库时可能会出错。因为 SQLite 数据库中并没有内置 CONCAT 函数，而是使用 || 运算符来实现字符串拼接。

因此，可以将查询语句中的 CONCAT 函数改为使用 || 运算符，示例代码如下：

string connectionString = "YourConnectionString"; // 数据库连接字符串
string query = "SELECT COUNT(CASE WHEN 季度 = 'Q1' THEN 1 ELSE NULL END) AS Q1Count, " +
               "COUNT(CASE WHEN 季度 = 'Q2' THEN 1 ELSE NULL END) AS Q2Count, " +
               "COUNT(CASE WHEN 季度 = 'Q3' THEN 1 ELSE NULL END) AS Q3Count, " +
               "COUNT(CASE WHEN 季度 = 'Q4' THEN 1 ELSE NULL END) AS Q4Count, " +
               "COUNT(*) AS TotalCount, " +
               "ROUND(SUM(CASE WHEN 季度 = 'Q1' THEN 1 ELSE 0 END)/COUNT(*)*100,2)||'%' AS Q1Percent, " +
               "ROUND(SUM(CASE WHEN 季度 = 'Q2' THEN 1 ELSE 0 END)/COUNT(*)*100,2)||'%' AS Q2Percent, " +
               "ROUND(SUM(CASE WHEN 季度 = 'Q3' THEN 1 ELSE 0 END)/COUNT(*)*100,2)||'%' AS Q3Percent, " +
               "ROUND(SUM(CASE WHEN 季度 = 'Q4' THEN 1 ELSE 0 END)/COUNT(*)*100,2)||'%' AS Q4Percent " +
               "FROM FAIsum " +
               "GROUP BY 季度";

DataTable dataTable = new DataTable();
using (SQLiteConnection connection = new SQLiteConnection(connectionString))
{
    SQLiteDataAdapter adapter = new SQLiteDataAdapter(query, connection);
    adapter.Fill(dataTable);
}

dataTable.Columns.Add("Q1Percent", typeof(string));
dataTable.Columns.Add("Q2Percent", typeof(string));
dataTable.Columns.Add("Q3Percent", typeof(string));
dataTable.Columns.Add("Q4Percent", typeof(string));

foreach (DataRow row in dataTable.Rows)
{
    double q1Count = Convert.ToDouble(row["Q1Count"]);
    double q2Count = Convert.ToDouble(row["Q2Count"]);
    double q3Count = Convert.ToDouble(row["Q3Count"]);
    double q4Count = Convert.ToDouble(row["Q4Count"]);
    double totalCount = Convert.ToDouble(row["TotalCount"]);

    row["Q1Percent"] = Math.Round(q1Count / totalCount * 100, 2) + "%";
    row["Q2Percent"] = Math.Round(q2Count / totalCount * 100, 2) + "%";
    row["Q3Percent"] = Math.Round(q3Count / totalCount * 100, 2) + "%";
    row["Q4Percent"] = Math.Round(q4Count / totalCount * 100, 2) + "%";
}

这里使用了 SQLiteConnection 和 SQLiteDataAdapter 类，同时将 CONCAT 函数改为使用 || 运算符。请注意，SQLite 中的 || 运算符是用于字符串拼接的，而不是逻辑运算。