How to insert and select from mysql simultaneously

Question

I have a requirement where I need to insert mobile number in mysql if and only if the number is is not present.So for this I am first checking if a number is present in mysql using select query .If number is not present then insert.Following is my code

PreparedStatement pt1=con.prepareStatement("select * from registerSmsUsers where mobile='"+mobile+"'");
PreparedStatement pt=con.prepareStatement("insert into registerSmsUsers values(?,?,?)");
        pt.setString(1, name);
        pt.setString(2, email);
        pt.setString(3, mobile);
ResultSet rs1=pt1.executeQuery();
        if(rs1.next())

{pt.executeUpdate();}

i dont know whether this is a efficient way or not.Please suggest me a better way then this

Answer 1

Probably the easiest way in mysql is:

insert ignore into registerSmsUsers values(?,?,?)

When assuming you have unique key on mobile

You may check it here: How to 'insert if not exists' in MySQL?

Or here: http://dev.mysql.com/doc/refman/5.6/en/insert.html

Answer 2

Many of the proposed solutions (including yours) have a race condition that can cause a primary key or unique constraint violation. You code also have a possible SQL injection attack by concatenating SQL rather than using prepared statement parameters. Use SELECT...FOR UPDATE.

PreparedStatement ps = con.prepareStatement("SELECT name, email, mobile FROM registerSmsUsers WHERE mobile=? FOR UPDATE",
                                            ResultSet.TYPE_FORWARD_ONLY,
                                            ResultSet.CONCUR_UPDATABLE);
ps.setString(1, mobile);
ResultSet rs = ps.executeQuery();
if (rs.next()) { // it exists already
   rs.moveToCurrentRow();
   rs.updateString(3, mobile);
   rs.updateRow();
} else { // it does NOT exist
   rs.moveToInsertRow();
   rs.updateString(1, name);
   rs.updateString(2, email);
   rs.updateString(3, mobile);
   rs.insertRow();
}
rs.close();
ps.close();

EDIT: Just make sure you have an index on registerSmsUsers.

CREATE INDEX registerSmsUsers_mobile_ndx ON registerSmsUsers(mobile)

or a unique contraint (which implicitly creates an index):

ALTER TABLE registerSmsUsers ADD CONSTRAINT registerSmsUsers_mobile_unq UNIQUE (mobile)

With an index, even with millions of records the update/insert will basically be instant.

EDIT2: Added cursor/result set options.

Answer 3

I think it would be better to create a stored procedure and then in that stored procedure you can first use the IF NOT EXISTS clause to check if the user exists using the select statement. If the user is not present you can insert the user in database.

Something like this:

IF NOT EXISTS(SELECT 1 FROM `registerSmsUsers` WHERE mobile= @mobile) THEN
    BEGIN
    INSERT INTO 
        `registerSmsUsers`
        (
            //column names
        ) 
        VALUES 
        (
            //values
        );
    END;
END IF;

Also there is a INSERT IGNORE statement which you can use like this:

insert ignore into registerSmsUsers values(?,?,?)

Answer 4

if not exists(select * from registerSmsUsers where mobile='232323') <-- will check your mobile no
begin
 insert into registerSmsUsers values(?,?,?)
end

This one is also an efficient way to check your method is also working fine but this also can be done See difference is you will have only one query here i hope this will help you thanks

[Edit]

Your questions answer

Ya there is a execution time diff between yours and mine query its depends upon a database size what you are using if you are using small size database (probably 1000 people) then you will not see any diff between your query and mine query but if your are using lakhs of users then your will have a performace issues check include execution plan in mysql you will get realtime difference between two

Answer 5

As requested, here is my tweaked version of brettw's answer:

import java.sql.*;

public class MySQLtest {

    public static void main(String[] args) {
        Connection con;
        try {
            con = DriverManager.getConnection(
                    "jdbc:mysql://192.168.1.3/zzzTest?" +
                    "useUnicode=yes&characterEncoding=UTF-8" +
                    "&user=root&password=whatever");
            String newName = "Gord";
            String newEmail = "gord@example.com";
            String newMobile = "416-555-1212";
            String sql = 
                    "SELECT " +
                        "id, " +
                        "name, " +
                        "email, " +
                        "mobile " +
                    "FROM registerSmsUsers " +
                    "WHERE mobile = ? " +
                    "FOR UPDATE";
            PreparedStatement pst = con.prepareStatement(
                    sql, 
                    ResultSet.TYPE_FORWARD_ONLY, 
                    ResultSet.CONCUR_UPDATABLE);
            pst.setString(1, newMobile);
            ResultSet rs = pst.executeQuery();
            if (rs.next()) {
                rs.moveToCurrentRow();
                rs.updateString("name", newName);
                rs.updateString("email", newEmail);
                rs.updateRow();
                System.out.println("Existing row updated.");
            }
            else {
                rs.moveToInsertRow();
                rs.updateString("name", newName);
                rs.updateString("email", newEmail);
                rs.updateString("mobile", newMobile);
                rs.insertRow();
                System.out.println("New row inserted.");
            }
        } catch (SQLException ex) {
            ex.printStackTrace();
        }
    }

}

Note that id is the Primary Key for the table: int(11) NOT NULL AUTO_INCREMENT