如何在VB中使用mysqlcommand执行sql变量

Question

我想做这样的查询。

SELECT @rownum:[email protected]+1 'rank' FROM (SELECT @rownum:=0) r 

当我在我的mysql查询浏览器上测试它时，它工作正常。

现在，我想用mysqlCommand在VB中执行它。当然@rownum被定义为一个参数并等待它的值。我怎样才能在VB中执行该查询？

Answer 1

您需要将变量添加到命令的参数：

command.Parameters.AddWithValue("@rownum", rownum) 

有些文档是在这里：http://dev.mysql.com/doc/refman/5.0/es/connector-net-examples-mysqlparametercollection.html

Answer 2

dim conn As New MySqlConnection <br> 
dim comm As New MySqlCommand<br><br> 
dim dAdapter As New MySqlDataAdapter<br> 
dim ddata As New DataSet<br> 

conn.ConnectionString = "DATABASE=" & ddatabase & ";SERVER=" & Trim(TextBox1.Text) & ";user id=dev;password=revolution;port=" & TextBox3.Text & " ;charset=utf8;<b>Allow User Variables=True" </b><br> 
conn.Open() <br> 
<br> 
comm.Connection = conn<br> 
comm.CommandText = "set @rownum = 10"<br> 
comm.ExecuteNonQuery() <br> 
<br> 
ddata.Clear()<br> 
ddata.Tables.Clear()<br> 
comm.Connection = conn<br> 
comm.CommandText = "select @rownum rownum"<br> 
dAdapter.SelectCommand = comm <br> 
dAdapter.Fill(ddata)<br> 
<br> 
msgbox(ddata.Tables(0).Rows(0).Item("rownum")) <br> 

Answer 3

必须把这个键添加到您的连接字符串：“允许用户变量= TRUE;”