检查OleDb表中是否存在列

Question

我试图检查列是否存在,如果不存在,请添加它.我尝试了几种解决方案,包括这个,但Access db的语法不正确.

这是我到目前为止:

    public void Update(string task, string dbPath, string tableName = "Frames")
    {
        OleDbConnection db = new OleDbConnection("Provider=Microsoft.JET.OLEDB.4.0;data source=" + dbPath);
        db.Open();

        OleDbCommand command = db.CreateCommand();
        command.CommandText = "COL_LENGTH('Frames','SetNumber')";
        Debug.WriteLine(command.ExecuteReader());




        /*
        string[] restrictions = new string[] {null, null, tableName};

        DataTable dtColumns = db.GetOleDbSchemaTable(OleDbSchemaGuid.Columns, restrictions);

        foreach (DataColumn column in dtColumns.Columns)
        {
            Debug.WriteLine(column.ColumnName);
        }*/

    }

我也尝试过使用GetOleDbSchemaTable,但它没有返回正确的表格或其他东西.我错过了什么？

Answer 1

要检查数据表中是否存在列,可以使用OleDbConnection的GetSchema方法

public void Update(string task, string dbPath, string colName, string tableName = "Frames") 
{ 
    using(OleDbConnection db = new OleDbConnection("........"))
    {
        db.Open(); 
        var schema = db.GetSchema("COLUMNS"); 
        var col = schema.Select("TABLE_NAME='" + tableName + 
                   " AND COLUMN_NAME='" + colName + "'" 

        if(col.Length > 0)
           // Column exist
        else
           // Column doesn't exist
}