尝试使用where子句中的like语句删除记录时，Advantage数据库将引发异常

Question

下面的代码显示当sql语句为：时，一条记录被删除：

select * from test where qty between 50 and 59  

但是sql语句：

select * from test where partno like 'PART/005%'

引发异常：

Advantage.Data.Provider.AdsException: Error 5072:  Action requires read-write access to the table

如何应用where子句可靠地删除记录？
注意：我使用的是Advantage Database v9.10.1.9，VS2008，.Net Framework 3.5和WinXP 32位

using System.IO;
using Advantage.Data.Provider;
using AdvantageClientEngine;
using NUnit.Framework;

namespace NetworkEidetics.Core.Tests.Dbf
{
  [TestFixture]
  public class AdvantageDatabaseTests
  {
    private const string DefaultConnectionString = @"data source={0};ServerType=local;TableType=ADS_CDX;LockMode=COMPATIBLE;TrimTrailingSpaces=TRUE;ShowDeleted=FALSE";
    private const string TestFilesDirectory = "./TestFiles";

    [SetUp]
    public void Setup()
    {
      const string createSql = @"CREATE TABLE [{0}] (ITEM_NO char(4), PARTNO char(20), QTY numeric(6,0), QUOTE numeric(12,4)) ";
      const string insertSql = @"INSERT INTO [{0}] (ITEM_NO, PARTNO, QTY, QUOTE) VALUES('{1}', '{2}', {3}, {4})";
      const string filename = "test.dbf";

      var connectionString = string.Format(DefaultConnectionString, TestFilesDirectory);

      using (var connection = new AdsConnection(connectionString)) {
        connection.Open();

        using (var transaction = connection.BeginTransaction()) {
          using (var command = connection.CreateCommand()) {
            command.CommandText = string.Format(createSql, filename);
            command.Transaction = transaction;
            command.ExecuteNonQuery();
          }

          transaction.Commit();
        }

        using (var transaction = connection.BeginTransaction()) {
          for (var i = 0; i < 1000; ++i) {
            using (var command = connection.CreateCommand()) {
              var itemNo = string.Format("{0}", i);
              var partNumber = string.Format("PART/{0:d4}", i);
              var quantity = i;
              var quote = i * 10;

              command.CommandText = string.Format(insertSql, filename, itemNo, partNumber, quantity, quote);
              command.Transaction = transaction;
              command.ExecuteNonQuery();
            }
          }
          transaction.Commit();
        }

        connection.Close();
      }
    }

    [TearDown]
    public void TearDown()
    {
      File.Delete("./TestFiles/test.dbf");
    }

    [Test]
    public void CanDeleteRecord()
    {
      const string sqlStatement = @"select * from test";

      Assert.AreEqual(1000, GetRecordCount(sqlStatement));
      DeleteRecord(sqlStatement, 3);
      Assert.AreEqual(999, GetRecordCount(sqlStatement));
    }

    [Test]
    public void CanDeleteRecordBetween()
    {
      const string sqlStatement = @"select * from test where qty between 50 and 59";

      Assert.AreEqual(10, GetRecordCount(sqlStatement));
      DeleteRecord(sqlStatement, 3);
      Assert.AreEqual(9, GetRecordCount(sqlStatement));
    }

    [Test]
    public void CanDeleteRecordWithLike()
    {
      const string sqlStatement = @"select * from test where partno like 'PART/005%'";

      Assert.AreEqual(10, GetRecordCount(sqlStatement));
      DeleteRecord(sqlStatement, 3);
      Assert.AreEqual(9, GetRecordCount(sqlStatement));
    }

    public int GetRecordCount(string sqlStatement)
    {
      var connectionString = string.Format(DefaultConnectionString, TestFilesDirectory);
      using (var connection = new AdsConnection(connectionString)) {
        connection.Open();

        using (var command = connection.CreateCommand()) {
          command.CommandText = sqlStatement;
          var reader = command.ExecuteExtendedReader();
          return reader.GetRecordCount(AdsExtendedReader.FilterOption.RespectFilters);
        }
      }
    }

    public void DeleteRecord(string sqlStatement, int rowIndex)
    {
      var connectionString = string.Format(DefaultConnectionString, TestFilesDirectory);
      using (var connection = new AdsConnection(connectionString)) {
        connection.Open();

        using (var command = connection.CreateCommand()) {
          command.CommandText = sqlStatement;

          var reader = command.ExecuteExtendedReader();

          reader.GotoBOF();
          reader.Read();

          if (rowIndex != 0) {
            ACE.AdsSkip(reader.AdsActiveHandle, rowIndex);
          }
          reader.DeleteRecord();
        }

        connection.Close();
      }
    }
  }
}

Answer 1

LIKE会生成静态游标而不是实时游标，这意味着它是只读数据集。要在这种情况下删除行，最好使用SQL DELETE语句。

DELETE FROM test where partno LIKE 'PART/005%'

我假设您的测试仅此而已。他们使用一些效率不高的机制来定位和删除行。

评论后更新，没有关键字段：

如何使用LEFT标量而不是LIKE（可能并非在所有情况下都适用，但对于您的示例适用）。如果大小始终相同，则还可以在左侧添加一个索引（partno，8）以提高性能：

select * from test where left(partno,8) = 'PART/005' 

然后，您可以直接在此实时结果集上使用扩展数据读取器的Delete功能（无需gotop和skip）。

在Alex的ROWID注释之后进行更新 我什至不知道我们的ROWID来自基表，即使在静态游标中也是如此。亚历克斯的评论是解决您的问题的方法。第一：

SELECT t.*, t.rowid FROM test t WHERE x LIKE 'PART/005%'

然后：

DELETE FROM test WHERE rowid = :thisid