Question 20682 in Mysql Question posted in
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How to validate so I would get message saying username already exists if I enter same username? – Mysql

exports.signup = async (req, res) => {
  const { username, password, name } = req.body;

  // TODO: Validate if username exists
  
  await knex("users").insert({ username, password, name });
  
  const user = await knex("users").where({ username }).first();

  // const users = await knex("users").where({username});
  
  
  // if (users === username) {
  //   res.status(401).json({
  //     error: {
  //       message: "Username already exists"
  //     }
  //   })
  // } else {
    const token = jwt.sign({ username, id: user.id }, secret);
    console.log(token);
    res.json({ ...user, token });
  // }
};

I can’t throw an error when I enter username which already exist in database mySQL. It keeps crashing the server and doesn;t reach else

It keeps crashing the server and doesn’t reach else.

exports.up = function (knex) {
  return knex.schema.createTable("users", (table) => {
    table.increments('id').primary();
    table.string("username").notNullable().unique();
    table.string("password").notNullable();
    table.string("name").notNullable();
  });
};

exports.down = function (knex) {
  return knex.schema.dropTable("users");
};

username is unique.

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2

Answers


  1. 0

    You can try - catch and analize the error code to see if it represents a unique key constraint violation in mySQL:

    exports.signup = async (req, res) => {
  const { username, password, name } = req.body;

  try {
    await knex('users').insert({ username, password, name });

    const user = await knex('users').where({ username }).first();

    const token = jwt.sign({ username, id: user.id }, secret);
    console.log(token);
    res.json({ ...user, token });
  } catch (err) {
    if (err.code === 'ER_DUP_ENTRY' || err.errno === 1062) {
      // User already exists...
    } else {
      // Server error...
    }
  }
};
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  2. 0

    Create unique constraint on username field in database.

    ALTER TABLE users ADD UNIQUE (username);

    And try again with same username it will throw error of duplicate entry.

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