Question

我想在表IF NOT EXISTS中执行INSERT

所以我有2个JTextField，我希望将变量添加到JTextfield的int表中，但条件是它们不存在于表中

这是代码，它给出了有关查询的错误：

try{
    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+db, "root", "123456");
       stmt = conn.createStatement();
       stmt.executeUpdate(
           "insert into router (edge01,edge02)\n" +
           "Select edge01, edge02 " +
           "Where not exists(select * from router " +
                            "where edge01='" + jTextField1.getText() +
                              "' and edge02='" + jTextField2.getText() + "')");
}
catch (SQLException ex) {
    Logger.getLogger(bdd.class.getName()).log(Level.SEVERE, null, ex);
}

错误：

SEVERE: null com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'Where not exists(select * from router where edge01='fffffffff' and edge02='fffff' at line 2

Answer 1

您的查询错误

try{
        Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/"+db, "root", "123456");
       stmt = conn.createStatement();
       stmt.executeUpdate("insert into router (edge01,edge02)\n" +
" Select edge01,edge02 Where <Some unique Field> not exists in(select "<Some unique Field>" from router where edge01='"+jTextField1.getText()+"' and edge02='"+jTextField2.getText()+"')");

}          catch (SQLException ex) {
               Logger.getLogger(bdd.class.getName()).log(Level.SEVERE, null, ex);
           }

Answer 2

首先选择数据以检查数据是否存在：'使用select * from router'。如果没有返回数据，则插入。

Answer 3

请尝试使用此查询：

insert into router (edge01,edge02)
 select edge01,edge02 from router where edge01 not in(select edge01 from router where    
       edge01='"+jTextField1.getText()+"' and edge02='"+jTextField2.getText()+"')"

如果不存在则插入表中

3 个答案: