Sequelize using MySQL dialect failed to generate foreign key while migrating models

Question

• I am using commands of sequelize to create and migrate Models to generate Tables in MySql database.
• To generate new model: sequelize model:create --name Demo --attributes column:string
• And After the Model and migration file generate, adding few lines of code to make association and foreign key constraints using given snippet of code:
• In Derived/Child Table of Comapny:

      Employee.associate = function (models) {
            // associations can be defined here
            Employee.belongsTo(models.Company, {
                foreignKey: "companyId",
                onDelete: "CASCADE"
            })
        };

• In Base/Parent table Comapany:

      Company.associate = function (models) {
          // associations can be defined here
          Company.hasMany(models.Employee,{
              foreignKey:"companyId",
          })
      };
  

But it does not reflect in Table->ALTER TABLE->ForeignKey Constraints.

Answer 1

Your foreign keys are messed up.... i think it should look something more like below because you want a field called companyId to be in your employee table that references the id field of the company table

Employee.associate = function (models) {
            // associations can be defined here
            Employee.belongsTo(models.Company, {
                sourceKey: "companyId",
                foreignKey: "id",
                onDelete: "CASCADE"
            })
        };

and

Company.associate = function (models) {
        // associations can be defined here
        Company.hasMany(models.Employee,{
            foreignKey:"companyId",
        })
    };

this one will just assume your source key is your primary key which is probably id

Answer 2

• The foreign key constraint will reflect to the MySQL DB and its table, only when we change migration file too along with model file.
• We have to add in migration file like:

  companyId:{
      type: Sequelize.INTEGER,
      onDelete: "CASCADE",
      references: {
          model: "Comapany",
          key: "id"
      }
    },
  

• It worked successfully for me.