[英]java.sql.SQLException: Before start of result set
在這里,我附加了代碼,它顯示了如下錯誤:java.sql.SQLException:
在開始結果集之前,我在這里做錯了什么:
String qry = "SELECT * From register ";
stmt = (PreparedStatement) conn.prepareStatement(qry);
rs = stmt.executeQuery();
while (rs.next()) {
String area = rs.getString("city");
if(city.equals(area)){
System.out.println("!!!!!!It matched: " + city);
String qry2="select state from register where city='"+city+"'";
System.out.println(qry2);
stmt = (PreparedStatement) conn.prepareStatement(qry2);
rs = stmt.executeQuery();
String state=rs.getString("state");
System.out.println("state: " + state);
break;
} else {
//System.out.println("No match with: " + area);
}
}
您可以在query1結果集循環內為query2使用新的ResultSet對象。
String qry2="select state from register where city='"+city+"'";
System.out.println(qry2);
stmt = (PreparedStatement) conn.prepareStatement(qry2);
ResultSet rs2 = stmt.executeQuery();
String state=rs2.getString("state");
但通常最好使用JDBC資源來遍歷結果集1,收集返回的所有“城市”值,然后循環遍歷“城市”結果,並調用query2以獲得與狀態2相關聯的“狀態”。 “城市”而非您所展示的方式。
您的代碼中不需要第二個結果集。 州和市都可以在同一結果集中找到。 您可以使用以下代碼:
String qry = "select * from register";
PreparedStatement stmt = (PreparedStatement) conn.prepareStatement(qry);
rs = stmt.executeQuery();
while (rs.next()) {
String area = rs.getString("city");
if(city.equals(area)){
System.out.println("!!!!!!It matched: " + city);
String state=rs.getString("state");
System.out.println("state: " + state);
break;
} else {
//System.out.println("No match with: " + area);
}
}
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