我目前正在制作一個(gè)程序，可以在其中刪除數(shù)據(jù)庫(kù)中的某些條目。我可以做到這一點(diǎn)，但我想添加一個(gè) JOptionPane 屏幕，以便它何時(shí)可以找到它或無(wú)法找到它（因此，當(dāng)未找到名稱時(shí)，不應(yīng)找到它并顯示一條消息說(shuō)找不到它）。我嘗試使用結(jié)果語(yǔ)句，但這似乎不起作用。如果有人知道如何做，請(qǐng)?jiān)u論如何做！private void btnDeleteActionPerformed(java.awt.event.ActionEvent evt) { ArrayList<Cookbook > recipes = new ArrayList(); String name = txtName.getText(); try { String url = "jdbc:derby://localhost:1527/Cookbook"; Connection conn = DriverManager.getConnection(url); String query = "DELETE from RECIPES WHERE NAME = ?"; PreparedStatement pst = conn.prepareStatement(query); pst.setString(1, name); pst.executeUpdate(); JOptionPane.showMessageDialog(null, name + " was sucessfully deleted"); } catch (Exception e) { JOptionPane.showMessageDialog(null, "was not found or could not be deleted"); }
1 回答
元芳怎么了
TA貢獻(xiàn)1798條經(jīng)驗(yàn) 獲得超7個(gè)贊
引用javadoc?executeUpdate()：
返回：
(1)?SQL 數(shù)據(jù)操作語(yǔ)言 (DML) 語(yǔ)句的行計(jì)數(shù)或 (2) 0（不返回任何內(nèi)容的 SQL 語(yǔ)句）
所以：
String url = "jdbc:derby://localhost:1527/Cookbook";
try (Connection conn = DriverManager.getConnection(url)) {
? ? String query = "DELETE from RECIPES WHERE NAME = ?";
? ? try (PreparedStatement pst = conn.prepareStatement(query)) {
? ? ? ? pst.setString(1, name);
? ? ? ? int rowCount = pst.executeUpdate();
? ? ? ? if (rowCount == 0) {
? ? ? ? ? ? JOptionPane.showMessageDialog(null, "'" + name + "' was not found");
? ? ? ? } else if (rowCount == 1) {
? ? ? ? ? ? JOptionPane.showMessageDialog(null, "'" + name + "' was successfully deleted");
? ? ? ? } else { // cannot happen if `NAME` has unique index in the database
? ? ? ? ? ? JOptionPane.showMessageDialog(null, rowCount + " recipes named '" + name + "' were deleted");
? ? ? ? }
? ? }
} catch (Exception e) {
? ? JOptionPane.showMessageDialog(null, "something went wrong: " + e);
}
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