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Johnny Pachecp
Asked: 2020-07-12 08:10:05 +0800 CST 2020-07-12 08:10:05 +0800 CST

How to modify the structure of a table with sequelize without deleting the data?

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I have a model made with sequelize , I can not delete the data from the institution table , but now I must add a day field to it .

I already tried sequelize.syncbut it does not modify the structure of the table. and sequelize.sync({force:true}) would delete all the data.

It is important that you do not delete anything since it is a database that must be modified as the project grows.

javascript

2 Answers

  1. The problem you raise (an evolving data model) is a common one. The solution I use in these cases is to create migrations .

    Cheers

    • 1
  2. Best Answer

    Using migrations is the most recommended way if you are in production. To perform a migration you simply need to write a file that exports an object with two functions:

    • up: transforms the current state of the models.
    • down: reverts some specific functionality.

    Note: this file must be in the migrations directory at the root of the project.

    These functions receive as a parameter an object of type QueryInterfaceand an instance of Sequelize. To make any type of change you want to do it in the up function .

    To change a column type just use the method changeColumn:

    module.exports = {
  up(queryInterface, sequelize) {
    return queryInterface.changeColumn('nombreModelo', 'nombreAtributo', {
      type: sequelize.<nuevo tipo>,
      // otros cambios
    });
  },
};

    Finally you must use the CLI to run your migration:

    Note: Install the sequelize-cli package if you don't already have it.

    sequelize db:migrate

    When the process is finished, your column should already be migrated. As a final recommendation, consult the documentation .

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