PreparedStatement 和 null 的问题

狐狸大仙 2003-10-21 01:09:01
sql = "select * from abcd where ? ";
PreparedStatement pstmt = conn.prepareStatement(sql);
setString(1,"name is null");

这样为什么不行呀?
如果要实现该怎么做?

当然在必要的时候,还要求能够
setString(1,"name = " + name);
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狐狸大仙 2003-10-21
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问题,还没有解决。
不过马上给分。
iamwls 2003-10-21
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sql = "select * from abcd where name = ?,aaa = ? ";
PreparedStatement pstmt = conn.prepareStatement(sql);
ps.setString(1,"NameYourSearch"); or ps.setNull(1,Types.STRING);
ps.setString(2,"aaa"); or ps.setNull(1,Types.STRING);
liad 2003-10-21
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Types.VARCHAR

???
狐狸大仙 2003-10-21
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我没有看到STRING,只有CHAR
我数据库里的数据类型是 VARCHAR2(15)
那我这里第二个参数应该写什么呀?
qiangchen 2003-10-21
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ChDw(米) 正确,第二个参数表示是string 类型的!值为 null 整句sql 意思为:select * from abcd where name is null
狐狸大仙 2003-10-21
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我看了一下 Types. 里没有STRING ,但是有CHAR。
能否具体讲解一下 setNull 的第二个参数是什么意思?
clapton 2003-10-21
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ChDw正解
pleonheart 2003-10-21
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你的sql写的不对,where 后面的条件是什么呢?
select * from abcd where name=?
ChDw 2003-10-21
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sql = "select * from abcd where name = ? ";
PreparedStatement pstmt = conn.prepareStatement(sql);
ps.setString(1,"NameYourSearch"); or ps.setNull(1,Types.STRING);
truezerg 2003-10-21
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你写的是什么啊? 看不懂你的意思
package cn.com.dao.chivementdao; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import cn.com.util.DBConnection; import cn.com.util.DBSql; import cn.com.vo.chivementvo.ChivementVo; public class ExamDao { private Connection conn = DBConnection.getConnectionOracle(); private ChivementVo examVo; public ExamDao() { } public ExamDao(ChivementVo examVo) { super(); this.examVo = examVo; } /** * 全部查询 */ public Object[][] selectAll() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_ALL); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumberAll(DBSql.SELECT_ALL_COUNT)][max]; while (rs.next()) { for (int j = 0; j < max; j++) { date[i][j] = rs.getObject(j + 1); } i++; } // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 根据学号查询 */ public Object[][] selectBySid() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_BY_S_ID); ps.setInt(1, examVo.getS_id()); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumber(DBSql.SELECT_BY_S_ID_COUNT, examVo .getS_id())][max]; while (rs.next()) { for (int j = 0; j < max; j++) { date[i][j] = rs.getObject(j + 1); } i++; } // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 根据组号查询 */ public Object[][] selectByGid() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_BY_G_ID); ps.setInt(1, examVo.getG_id()); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumber(DBSql.SELECT_BY_G_ID_COUNT, examVo .getG_id())][max]; while (rs.next()) { for (int j = 0; j < max; j++) { date[i][j] = rs.getObject(j + 1); } i++; } // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 根据课程号查询 */ public Object[][] selectByCid() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_BY_C_ID); ps.setInt(1, examVo.getC_id()); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumber(DBSql.SELECT_BY_C_ID_COUNT, examVo .getC_id())][max]; while (rs.next()) { for (int j = 0; j < max; j++) { // System.out.println( examVo.getG_id()); date[i][j] = rs.getObject(j+1); } i++; } // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 根据姓名模糊查询 * * @return */ public Object[][] selectByName() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_BY_S_NAME); ps.setString(1, examVo.getS_name()); ps.setString(2, "%" + examVo.getS_name() + "%"); ps.setString(3, "%" + examVo.getS_name()); ps.setString(4, examVo.getS_name() + "%"); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumberByName(DBSql.SELECT_BY_S_NAME_COUNT, examVo.getS_name())][max]; while (rs.next()) { for (int j = 0; j < max; j++) { date[i][j] = rs.getObject(j + 1); } i++; } } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 根据课程名称模糊查询 * * @return */ public Object[][] selectByClassName() { Object date[][] = null; int max = 0; int i = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.SELECT_BY_CLASS_NAME); ps.setString(1, examVo.getClass_name()); ps.setString(2, "%" + examVo.getClass_name() + "%"); ps.setString(3, "%" + examVo.getClass_name()); ps.setString(4, examVo.getClass_name() + "%"); rs = ps.executeQuery(); // 得到列数 max = rs.getMetaData().getColumnCount(); date = new Object[getnumberByName(DBSql.SELECT_BY_CLASS_COUNT, examVo.getClass_name())][max]; while (rs.next()) { for (int j = 0; j < max; j++) { date[i][j] = rs.getObject(j + 1); } i++; } } catch (SQLException e) { e.printStackTrace(); } return date; } /** * 修改选中学生的成绩 * */ public void updatSelectClass() { PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(DBSql.UPDATE_EXAM_BY_STUID); ps.setInt(1, examVo.getClassExamChivement()); ps.setInt(2, examVo.getS_id()); ps.setInt(3, examVo.getC_id()); ps.executeUpdate(); } catch (SQLException e) { e.printStackTrace(); } } /** * 得到所有课程号和课程名 * * @return */ public String[] getClassNoName() { String[] classNoName = null; PreparedStatement ps = null; ResultSet rs = null; int j = 0; try { int i = getnumberAll(DBSql.SELECT_CLASS_NAME_COUNT); classNoName = new String[i + i]; ps = conn.prepareStatement(DBSql.SELECT_CLASS_NAME); rs = ps.executeQuery(); while (rs.next()) { classNoName[j] = rs.getString(1); classNoName[j + i] = rs.getString(2); j++; } } catch (SQLException e) { e.printStackTrace(); } return classNoName; } /** * 根据科目修改成绩 查询学号 姓名 成绩 * */ public void SelectClassStuName() { int i = 0; PreparedStatement ps = null; ResultSet rs = null; int j = getnumberBySelectClassName( DBSql.SELECT_CLASS_STU_SNO_SNAME_EXAM_COUNT, examVo.getC_id()); int[] sNum = new int[j]; String[] sName = new String[j]; int[] classExam = new int[j]; try { ps = conn.prepareStatement(DBSql.SELECT_CLASS_STU_SNO_SNAME_EXAM); ps.setInt(1, examVo.getC_id()); rs = ps.executeQuery(); while (rs.next()) { sNum[i] = rs.getInt(1); sName[i] = rs.getString(2); classExam[i] = rs.getInt(3); i++; } } catch (SQLException e) { e.printStackTrace(); } examVo.setSid(sNum); examVo.setSname(sName); examVo.setClassExam(classExam); } /** * 根据科目修改成绩 查询学号 姓名 成绩 后修改成绩 * */ public void UpdateClassStuName() { // int i = 0; PreparedStatement ps = null; ResultSet rs = null; int j = getnumberBySelectClassName( DBSql.SELECT_CLASS_STU_SNO_SNAME_EXAM_COUNT, examVo.getC_id()); try { ps = conn.prepareStatement(DBSql.UPDATE_CHIVEMENT_BY_CLASS); for(int i =0;iparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(str); rs = ps.executeQuery(); rs.next(); number = rs.getInt(1); // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return number; } /** * 根据学号 根据组号 根据课程号查询 获得行数 * * @return */ public int getnumber(String str, int i) { int number = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(str); ps.setInt(1, i); rs = ps.executeQuery(); rs.next(); number = rs.getInt(1); // rs.close(); // ps.close(); // conn.close(); } catch (SQLException e) { e.printStackTrace(); } return number; } /** * 根据姓名 课程名 查询 获得行数 * */ public int getnumberByName(String str, String i) { int number = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(str); ps.setString(1, i); ps.setString(2, "%" + i + "%"); ps.setString(3, "%" + i); ps.setString(4, i + "%"); rs = ps.executeQuery(); rs.next(); number = rs.getInt(1); } catch (SQLException e) { e.printStackTrace(); } return number; } // /** // * 根据课程名查询 获得行数 // * // */ // // public int getnumberByClassName(String str, String i) { // int number = 0; // PreparedStatement ps = null; // ResultSet rs = null; // try { // ps = conn.prepareStatement(str); // ps.setString(1, i); // ps.setString(2, "%" + i + "%"); // ps.setString(3, "%" + i); // ps.setString(4, i + "%"); // rs = ps.executeQuery(); // rs.next(); // number = rs.getInt(1); // } catch (SQLException e) { // e.printStackTrace(); // } // return number; // } /** * * 根据课程名修改成绩获得行数 * * @param str * @param i * @return */ public int getnumberBySelectClassName(String str, int i) { int number = 0; PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement(str); ps.setInt(1, i); rs = ps.executeQuery(); rs.next(); number = rs.getInt(1); } catch (SQLException e) { e.printStackTrace(); } return number; } }

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