[英]Correct way to find rowcount in Java JDBC
我嘗試了不同的方法來獲取 java JDBC 中的行數,但似乎沒有一個給出正確的結果。 我做錯了什么嗎?
即使客戶表是空的並且我應該將行數設為 0,但我不明白為什么我會得到一個非零行數值。
方法1 -
query = "SELECT * FROM customer WHERE username ='"+username+"'";
rs = stmt.executeQuery(query);
ResultSetMetaData metaData = rs.getMetaData();
rowcount = metaData.getColumnCount();
方法2 -
query = "SELECT * FROM customer WHERE username ='"+username+"'";
rs = stmt.executeQuery(query);
rowcount = rs.last() ? rs.getRow() : 0;
請看這段代碼:
import java.io.*;
import java.sql.*;
public class CountRows{
public static void main(String[] args) {
System.out.println("Count number of rows in a specific table!");
Connection con = null;
int count = 0;
try {
Class.forName("com.mysql.jdbc.Driver");
con = DriverManager.getConnection("jdbc:mysql://localhost:3306/jdbctutorial","root","root");
try {
Statement st = con.createStatement();
BufferedReader bf = new BufferedReader(new InputStreamReader(System.in));
System.out.println("Enter table name:");
String table = bf.readLine();
ResultSet res = st.executeQuery("SELECT COUNT(*) FROM "+table);
while (res.next()){
count = res.getInt(1);
}
System.out.println("Number of row:"+count);
}
catch (SQLException s){
System.out.println("SQL statement is not executed!");
}
}
catch (Exception e){
e.printStackTrace();
}
}
}
這是我用來在 Java 中獲取行數的方式:
String query = "SELECT * FROM yourtable";
Statement st = sql.createStatement( ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY );
ResultSet rs = st.executeQuery(query);
int rows = 0;
rs.last();
rows = rs.getRow();
rs.beforeFirst();
System.out.println("Your query have " + rows + " rows.");
當您使用不支持TYPE_FORWARD_ONLY
的 JDBC 時,請使用此方法獲取行數。
Statement s = cd.createStatement();
ResultSet r = s.executeQuery("SELECT COUNT(*) AS rowcount FROM TableName");
r.next();
int count = r.getInt("rowcount");
r.close();
System.out.println("MyTable has " + count + " row(s).");
您可以使用上述方法獲取行數。
謝謝..
在 Android 中,沒有結果會返回錯誤。 因此,在while(resultset.next())中增加計數之前檢查這種情況
if(resultset!=null)
{
//proceed with incrementing row count function
}
else
{
// No resultset found
}
只需迭代和計數
ResultSet result = sta.executeQuery("SELECT * from A3");
int k=0;
while(result.next())
k++;
System.out.print(k); //k is the no of row
由於方法名稱指定metaData.getColumnCount()
將返回結果集中的總列數,但不返回總行數(計數)。
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