本文介绍了java mysql count行数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
我创建了这段代码,允许我计算表格中的行数。但是,我无法返回计数的数字,并显示无法从结果类型为void的方法返回值。有人能告诉我'我的错误在哪里?非常感谢!
I created this code to allow me calculate the number of rows in my table. However, I'm not able to return the counted number with an error saying "cannot return a value from method whose result type is void." Could someone show me where' my error? Thanks alot!
public void num() throws Exception {
try {
// This will load the MySQL driver, each DB has its own driver
Class.forName("com.mysql.jdbc.Driver");
// Setup the connection with the DB
connect = DriverManager.getConnection("jdbc:mysql://localhost/testdb?"
+ "user=root&password=");
// Statements allow to issue SQL queries to the database
statement = connect.createStatement();
resultSet = statement.executeQuery("select * from testdb.emg");
int count = 0;
while (resultSet.next()) {
count++;
}
return count;
} catch (Exception e) {
}
推荐答案
尝试以下代码
public int num() throws Exception {
try {
// This will load the MySQL driver, each DB has its own driver
Class.forName("com.mysql.jdbc.Driver");
// Setup the connection with the DB
connect = DriverManager.getConnection("jdbc:mysql://localhost/testdb?"
+ "user=root&password=");
// Statements allow to issue SQL queries to the database
statement = connect.createStatement();
resultSet = statement.executeQuery("select count(*) from testdb.emg");
while (resultSet.next()) {
return resultSet.getInt(1);
}
} catch (Exception e) {
}
以下是错误
-
public void num()抛出异常{
应该是
public int num()抛出异常{
要计算总行数,您应该使用查询从testdb.emg中选择count(*)
For counting total rows you should use query select count(*) from testdb.emg
让我知道任何问题。
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