如何为 MS Access 编写区分大小写的查询? [英] How to write Case Sensitive Query for MS Access?

问题描述

我想知道区分大小写的 MS Access 选择查询.

I want to know the Select Query for MS Access with case sensitive.

我有两个 VitualMonitorName 值如下

I have two values for VitualMonitorName as below

VCode VirtualMonitorName
Row 1 (1, 'VM1');
Row 2 (2, 'Vm1');

这里两个值不同.

如果我写

"SELECT VCode FROM VirtualMaster WHERE VirtualMonitorName like '" + Vm1 + "'";

它只回复 VCode = 1.

It replies VCode = 1 Only.

推荐答案

您可以使用 StrComp() 函数和 vbBinaryCompare 进行区分大小写的比较.下面是来自立即窗口的示例，用于显示 StrComp() 的工作原理.有关详细信息，请参阅 Access 帮助主题.

You can use the StrComp() function with vbBinaryCompare for a case-sensitive comparison. Here is an example from the Immediate window to show how StrComp() works. See the Access help topic for more details.

? StrComp("a", "A", vbBinaryCompare)
 1 

? StrComp("a", "A",vbTextCompare)
0

StrComp() 如果前两个参数计算结果相等，则返回 0，如果它们不相等，则返回 1 或 -1，如果任一参数为 Null，则返回 Null.

StrComp() returns 0 if the first two arguments evaluate as equal, 1 or -1 if they are unequal, and Null if either argument is Null.

要在查询中使用该函数，请提供 vbBinaryCompare 常量的值 (0) 而不是其名称.

To use the function in a query, supply the vbBinaryCompare constant's value (0) rather than its name.

SELECT VCode
FROM VirtualMaster
WHERE StrComp(VirtualMonitorName, "Vm1", 0) = 0;

如果其他应用程序使用较新的访问数据库引擎 (ACE") 驱动程序，则此方法也可用于来自其他应用程序的查询.比如下面的C#代码

This approach is also available to queries from other applications if they use the newer Access Database Engine ("ACE") drivers. For example, the following C# code

string myConnectionString =
        @"Driver={Microsoft Access Driver (*.mdb, *.accdb)};" +
        @"Dbq=C:UsersPublicDatabase1.accdb;";
using (OdbcConnection con = new OdbcConnection(myConnectionString))
{
    con.Open();
    using (var cmd = new OdbcCommand())
    {
        cmd.Connection = con;
        cmd.CommandText = 
                "SELECT COUNT(*) AS n FROM [VirtualMaster] " +
                "WHERE StrComp([VirtualMonitorName],?,?) = 0";
        cmd.Parameters.AddWithValue("?", "Vm1");
        cmd.Parameters.Add("?", OdbcType.Int);

        var vbCompareOptions = new Dictionary<string, int>() 
        {
            {"vbBinaryCompare", 0},
            {"vbTextCompare", 1}
        };
        string currentOption = "";

        currentOption = "vbBinaryCompare";
        cmd.Parameters[1].Value = vbCompareOptions[currentOption];
        Console.WriteLine(
                "{0} found {1} record(s)", 
                currentOption, 
                Convert.ToInt32(cmd.ExecuteScalar()));

        currentOption = "vbTextCompare";
        cmd.Parameters[1].Value = vbCompareOptions[currentOption];
        Console.WriteLine(
                "{0} found {1} record(s)",
                currentOption,
                Convert.ToInt32(cmd.ExecuteScalar()));
    }
}

生产

vbBinaryCompare found 1 record(s)
vbTextCompare found 2 record(s)

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