有人可以解释正确的方法吗？当使用（WHERE）＆＃34; OR＆＃34;？
时，我们如何传递参数？"SELECT ... WHERE paraX=? OR paraY=?";
我尝试使用以下代码，但它们不会执行。
pstm.setString(1, 1st_para);
pstm.setString(2, 2nd_para);
（请注意我是JAVA和Preparedstatement的初学者）
感谢名单！
答案 0 :(得分：3)
作为Java初学者，请查看以下代码：DB表：
CREATE TABLE `employee` (
`emp_id` INT NOT NULL AUTO_INCREMENT,
`emp_name` VARCHAR(45) NOT NULL,
`salary` DECIMAL NULL,
`age` INT NULL,
PRIMARY KEY (`emp_id`));
INSERT INTO `employee` (`emp_name`, `salary`, `age`) VALUES ('Abc', '100.23', '23');
INSERT INTO `employee` (`emp_name`, `salary`, `age`) VALUES ('Def', '220.2', '34');
INSERT INTO `employee` (`emp_name`, `salary`, `age`) VALUES ('Pqr', '50.44', '12');
INSERT INTO `employee` (`emp_name`, `salary`, `age`) VALUES ('Xyz', '75.66', '20');
INSERT INTO `employee` (`emp_name`, `salary`, `age`) VALUES ('Lmn', '150.0', '30');
获取mysql-connector-java依赖关系（使用Maven，或将其包含在classpath中）。基本代码：
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class PreparedStatementDemo {
public static void main(String[] args) {
try {
Class.forName("com.mysql.jdbc.Driver");
} catch (ClassNotFoundException e) {
System.err.println("No driver found..");
}
try {
Connection conn =
DriverManager.getConnection("jdbc:mysql://${host}:${port}/${dbname}", "${username}", "${password}");
PreparedStatement prepareStatement =
conn.prepareStatement("SELECT * FROM employee WHERE salary > ? AND age > ?");
prepareStatement.setDouble(1, 75.0);
prepareStatement.setInt(2, 20);
ResultSet resultSet = prepareStatement.executeQuery();
int i = 1;
while (resultSet.next()) {
System.out.println("Row: " + i);
System.out.println("\tId: " + resultSet.getInt(1));
System.out.println("\tName: " + resultSet.getString(2));
System.out.println("\tSalary: " + resultSet.getDouble(3));
System.out.println("\tAge: " + resultSet.getInt(4));
i++;
}
prepareStatement.close();
conn.close();
} catch (SQLException e) {
System.err.println("Error in DB communication: " + e.getMessage());
}
}
}
编辑连接字符串的值。 PreparedStatement接受索引从1开始的运行时值。 ResultSet也是如此。
答案 1 :(得分：0)
"SELECT ... WHERE paraX=? OR paraY=?";
pstm.setString(1, "1st_Text");
pstm.setString(2, "2nd_Text");
我发现了问题，我的编码错误发生了错误。 '因为我在TextArea的ActionForforme中调用了该方法。但必须在KeyReleased Area中调用它。所以，代码是正确的。为什么我之前没有提到过代码，'因为这只是一种方法，但我还没有完成编码..
感谢所有宝贵的时间，你浪费了我的问题..
public static void FillAttendsTable(JTable table, String valueToSearch) throws Exception {
clasid = jTextField_Class_ID.getText();
studid = jTextField_Stud_ID.getText();
if((!clasid.equals("") && studid.equals("")) || (clasid.equals("") && !studid.equals(""))){
cs = " AND (cs.clas_id = ? OR cs.stud_id = ?)";
}else if(!clasid.equals("") && !studid.equals("")){
cs = " AND cs.clas_id = ? AND s.stud_id = ?";
}else if(clasid.equals("") && studid.equals("")){
cs = " AND CONCAT(c.clas_gred,clas_stat,clas_end,c.note,stud_fnem)LIKE ?";
}
Connection conc = Config.DBConnector.getConnection();
if(jCheckBox_Present.isSelected() && (!clasid.equals("") || !studid.equals(""))){
qri = "SELECT DISTINCT cs.clas_id,c.clas_gred,s.stud_id,stud_fnem,stud_lnem,a.atn_date,clas_stat,clas_end FROM (((tbl_clas_stud AS cs JOIN tbl_student As s ON cs.stud_id = s.stud_id) JOIN tbl_class AS c ON cs.clas_id = c.clas_id) JOIN tbl_attends AS a ON a.clas_id=cs.clas_id) WHERE NOT EXISTS (SELECT a.stud_id FROM tbl_attends AS a WHERE cs.stud_id=a.stud_id)"+cs;
num = "1";
pstm = (PreparedStatement) conc.prepareStatement(qri);
pstm.setString(1, clasid);
pstm.setString(2, studid);
}else if(jCheckBox_Absent.isSelected() && (!clasid.equals("") || !studid.equals(""))){
qri = "SELECT DISTINCT cs.clas_id,c.clas_gred,s.stud_id,stud_fnem,stud_lnem,a.atn_date,clas_stat,clas_end FROM (((tbl_clas_stud AS cs JOIN tbl_student As s ON cs.stud_id = s.stud_id) JOIN tbl_class AS c ON cs.clas_id = c.clas_id) JOIN tbl_attends AS a ON a.clas_id=cs.clas_id) WHERE EXISTS (SELECT a.stud_id FROM tbl_attends AS a WHERE cs.stud_id=a.stud_id)"+cs;
num = "0";
pstm = (PreparedStatement) conc.prepareStatement(qri);
pstm.setString(1, clasid);
pstm.setString(2, studid);
}else if(jCheckBox_Absent.isSelected()) {
qri = "SELECT DISTINCT cs.clas_id,c.clas_gred,s.stud_id,stud_fnem,stud_lnem,a.atn_date,clas_stat,clas_end FROM (((tbl_clas_stud AS cs JOIN tbl_student As s ON cs.stud_id = s.stud_id) JOIN tbl_class AS c ON cs.clas_id = c.clas_id) JOIN tbl_attends AS a ON a.clas_id=cs.clas_id) WHERE EXISTS (SELECT a.stud_id FROM tbl_attends AS a WHERE cs.stud_id=a.stud_id)"+cs;
num = "0";
pstm = (PreparedStatement) conc.prepareStatement(qri);
pstm.setString(1, "%" + valueToSearch + "%");
}else if(jCheckBox_Present.isSelected()) {
qri = "SELECT DISTINCT cs.clas_id,c.clas_gred,s.stud_id,stud_fnem,stud_lnem,a.atn_date,clas_stat,clas_end FROM (((tbl_clas_stud AS cs JOIN tbl_student As s ON cs.stud_id = s.stud_id) JOIN tbl_class AS c ON cs.clas_id = c.clas_id) JOIN tbl_attends AS a ON a.clas_id=cs.clas_id) WHERE NOT EXISTS (SELECT a.stud_id FROM tbl_attends AS a WHERE cs.stud_id=a.stud_id)"+cs;
num = "1";
pstm = (PreparedStatement) conc.prepareStatement(qri);
pstm.setString(1, "%" + valueToSearch + "%");
}
ResultSet rs = pstm.executeQuery();
DefaultTableModel dtm = (DefaultTableModel) table.getModel();
dtm.setRowCount(0);
Object[] row;
while (rs.next()) {
row = new Object[9];
row[0] = rs.getString(1);
row[1] = rs.getString(2);
row[2] = rs.getString(3);
row[3] = rs.getString(4);
row[4] = rs.getString(5);
row[5] = rs.getString(6);
row[6] = rs.getString(7);
row[7] = rs.getString(8);
row[8] = num;
dtm.addRow(row);
}
}