如何编写区分大小写的MS Access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.

我有如下两个VitualMonitorName值

I have two values for VitualMonitorName as below

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

这两个值都不同.

如果我写

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

它仅回复VCode = 1.

It replies VCode = 1 Only.

推荐答案

您可以将StrComp()函数与vbBinaryCompare一起使用，以进行区分大小写的比较.这是即时"窗口中的示例，用于显示StrComp()的工作方式.有关更多详细信息，请参见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

如果前两个参数的值相等，则

StrComp()返回0；如果两个参数不相等，则返回1或-1；如果其中一个参数为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更新的Access Database Engine("ACE")驱动程序，则这些方法也可用于它们.例如，以下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:\Users\Public\Database1.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()));
    }
}

产生

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

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