[英]How to get the number of columns from a JDBC ResultSet?
您可以从ResultSetMetaData获取列号:
Statement st = conn.createStatement();
ResultSet rs = st.executeQuery(query);
ResultSetMetaData rsmd = rs.getMetaData();
int columnsNumber = rsmd.getColumnCount();
PreparedStatement ps=con.prepareStatement("select * from stud");
ResultSet rs=ps.executeQuery();
ResultSetMetaData rsmd=rs.getMetaData();
System.out.println("columns: "+rsmd.getColumnCount());
System.out.println("Column Name of 1st column: "+rsmd.getColumnName(1));
System.out.println("Column Type Name of 1st column: "+rsmd.getColumnTypeName(1));
您可以使用代码获得的结果集中的列数(因为 DB 使用的是 PostgreSQL):
//load the driver for PostgreSQL Class.forName("org.postgresql.Driver"); String url = "jdbc:postgresql://localhost/test"; Properties props = new Properties(); props.setProperty("user","mydbuser"); props.setProperty("password","mydbpass"); Connection conn = DriverManager.getConnection(url, props); //create statement Statement stat = conn.createStatement(); //obtain a result set ResultSet rs = stat.executeQuery("SELECT c1, c2, c3, c4, c5 FROM MY_TABLE"); //from result set give metadata ResultSetMetaData rsmd = rs.getMetaData(); //columns count from metadata object int numOfCols = rsmd.getColumnCount();
但是您可以获得有关列的更多元信息:
for(int i = 1; i <= numOfCols; i++)
{
System.out.println(rsmd.getColumnName(i));
}
在建立连接并执行查询后,试试这个:
ResultSet resultSet;
int columnCount = resultSet.getMetaData().getColumnCount();
System.out.println("column count : "+columnCount);
这将在列中打印数据,并在到达最后一列后换行。
ResultSetMetaData resultSetMetaData = res.getMetaData();
int columnCount = resultSetMetaData.getColumnCount();
for(int i =1; i<=columnCount; i++){
if(!(i==columnCount)){
System.out.print(res.getString(i)+"\t");
}
else{
System.out.println(res.getString(i));
}
}
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