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The Comprehensive Sequelize Cheatsheet
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Sequelize is the most famous Node ORM and is quite feature-rich, but while using it I spend much of my time juggling around between the documentation and different google searches.
This Cheatsheet is the one that I always wanted but was never able to find.
See any error or anything missing? Comment below, or better, send a pull request to the repo linked in the end.
npm install --save sequelize
You also need to install the driver for the database you're using.
# One of the following:
npm install --save pg pg-hstore # Postgres If node version < 14 use pg@7.12.1 instead
npm install --save mysql2
npm install --save mariadb
npm install --save sqlite3
npm install --save tedious # Microsoft SQL Server
A Sequelize instance must be created to connect to the database. By default, this connection is kept open and used for all the queries but can be closed explicitly.
const Sequelize = require('sequelize');
// Option 1: Passing parameters separately
const sequelize = new Sequelize('database', 'username', 'password', {
host: 'localhost',
dialect: /* one of 'mysql' | 'mariadb' | 'postgres' | 'mssql' */
});
// Option 2: Passing a connection URI
const sequelize = new Sequelize('postgres://user:pass@example.com:5432/dbname');
// For SQLite, use this instead
const sequelize = new Sequelize({
dialect: 'sqlite',
storage: 'path/to/database.sqlite'
});
For more detailed information about connecting to different dialects, check out the official docs
.authenticate()
can be used with the created instance to check whether the connection is working.
sequelize
.authenticate()
.then(() => {
console.log("Connection has been established successfully.");
})
.catch((err) => {
console.error("Unable to connect to the database:", err);
});
sequelize.close();
To define mappings between Model and Table, we can use the .define()
method
To set up a basic model with only attributes and their datatypes
const ModelName = sequelize.define("tablename", {
// s will be appended automatically to the tablename
firstColumn: Sequelize.INTEGER,
secondColumn: Sequelize.STRING,
});
For getting a list of all the data types supported by Sequelize, check out the official docs
Apart from datatypes, many other options can also be set on each column
const ModelName = sequelize.define("tablename", {
firstColumn: {
// REQUIRED
type: Sequelize.INTEGER,
// OPTIONAL
allowNull: false, // true by default
defaultValue: 1,
primaryKey: true, // false by default
autoIncrement: true, // false by default
unique: true,
field: "first_column", // To change the field name in actual table
},
});
To create a composite unique key, give the same name to the constraint in all the columns you want to include in the composite unique key
const ModelName = sequelize.define("tablename", {
firstColumn: {
type: Sequelize.INTEGER,
unique: "compositeIndex",
},
secondColumn: {
type: Sequelize.INTEGER,
unique: "compositeIndex",
},
});
They can also be created using indexes
const ModelName = sequelize.define(
"tablename",
{
firstColumn: Sequelize.INTEGER,
secondColumn: Sequelize.INTEGER,
},
{
indexes: [
{
unique: true,
fields: ["firstColumn", "secondColumn"],
},
],
}
);
Getters can be used to get the value of the column after some processing.
Setters can be used to process the value before saving it into the table.
const Employee = sequelize.define("employee", {
name: {
type: Sequelize.STRING,
allowNull: false,
get() {
const title = this.getDataValue("title");
// 'this' allows you to access attributes of the instance
return this.getDataValue("name") + " (" + title + ")";
},
},
title: {
type: Sequelize.STRING,
allowNull: false,
set(val) {
this.setDataValue("title", val.toUpperCase());
},
},
});
Employee.create({ name: "John Doe", title: "senior engineer" }).then(
(employee) => {
console.log(employee.get("name")); // John Doe (SENIOR ENGINEER)
console.log(employee.get("title")); // SENIOR ENGINEER
}
);
For more in-depth information about Getters and Setters, check out the official docs
Validations are automatically run on create
, update
and save
const ModelName = sequelize.define("tablename", {
firstColumn: {
type: Sequelize.STRING,
validate: {
is: ["^[a-z]+$", "i"], // will only allow letters
is: /^[a-z]+$/i, // same as the previous example using real RegExp
not: ["[a-z]", "i"], // will not allow letters
isEmail: true, // checks for email format (foo@bar.com)
isUrl: true, // checks for url format (http://foo.com)
isIP: true, // checks for IPv4 (129.89.23.1) or IPv6 format
isIPv4: true, // checks for IPv4 (129.89.23.1)
isIPv6: true, // checks for IPv6 format
isAlpha: true, // will only allow letters
isAlphanumeric: true, // will only allow alphanumeric characters, so "_abc" will fail
isNumeric: true, // will only allow numbers
isInt: true, // checks for valid integers
isFloat: true, // checks for valid floating point numbers
isDecimal: true, // checks for any numbers
isLowercase: true, // checks for lowercase
isUppercase: true, // checks for uppercase
notNull: true, // won't allow null
isNull: true, // only allows null
notEmpty: true, // don't allow empty strings
equals: "specific value", // only allow a specific value
contains: "foo", // force specific substrings
notIn: [["foo", "bar"]], // check the value is not one of these
isIn: [["foo", "bar"]], // check the value is one of these
notContains: "bar", // don't allow specific substrings
len: [2, 10], // only allow values with length between 2 and 10
isUUID: 4, // only allow uuids
isDate: true, // only allow date strings
isAfter: "2011-11-05", // only allow date strings after a specific date
isBefore: "2011-11-05", // only allow date strings before a specific date
max: 23, // only allow values <= 23
min: 23, // only allow values >= 23
isCreditCard: true, // check for valid credit card numbers
// Examples of custom validators:
isEven(value) {
if (parseInt(value) % 2 !== 0) {
throw new Error("Only even values are allowed!");
}
},
},
},
});
const ModelName = sequelize.define(
"tablename",
{
firstColumn: Sequelize.INTEGER,
secondColumn: Sequelize.INTEGER,
},
{
validate: {
// Define your Model Wide Validations here
checkSum() {
if (this.firstColumn + this.secondColumn < 10) {
throw new Error("Require sum of columns >=10");
}
},
},
}
);
const ModelName = sequelize.define(
"tablename",
{
firstColumn: Sequelize.INTEGER,
},
{
timestamps: true, // Enable timestamps
createdAt: false, // Don't create createdAt
updatedAt: false, // Don't create updatedAt
updatedAt: "updateTimestamp", // updatedAt should be called updateTimestamp
}
);
Sequelize can automatically create the tables, relations and constraints as defined in the models
ModelName.sync(); // Create the table if not already present
// Force the creation
ModelName.sync({ force: true }); // this will drop the table first and re-create it afterwards
ModelName.drop(); // drop the tables
You can manage all models at once using sequelize instead
sequelize.sync(); // Sync all models that aren't already in the database
sequelize.sync({ force: true }); // Force sync all models
sequelize.sync({ force: true, match: /_test$/ }); // Run .sync() only if database name ends with '_test'
sequelize.drop(); // Drop all tables
Sequelize Models are ES6 classes. We can easily add custom instance or class level methods.
const ModelName = sequelize.define("tablename", {
firstColumn: Sequelize.STRING,
secondColumn: Sequelize.STRING,
});
// Adding a class level method
ModelName.classLevelMethod = function () {
return "This is a Class level method";
};
// Adding a instance level method
ModelName.prototype.instanceLevelMethod = function () {
return [this.firstColumn, this.secondColumn].join(" ");
};
const User = sequelize.define(
"User",
{
/* attributes */
},
{
indexes: [
// Create a unique index on email
{
unique: true,
fields: ["email"],
},
// Creates a gin index on data with the jsonb_path_ops operator
{
fields: ["data"],
using: "gin",
operator: "jsonb_path_ops",
},
// By default index name will be [table]_[fields]
// Creates a multi column partial index
{
name: "public_by_author",
fields: ["author", "status"],
where: {
status: "public",
},
},
// A BTREE index with an ordered field
{
name: "title_index",
using: "BTREE",
fields: [
"author",
{
attribute: "title",
collate: "en_US",
order: "DESC",
length: 5,
},
],
},
],
}
);
There are four types of definitions. They are used in pairs.
For the example lets define two Models
const Foo = sequelize.define("foo" /* ... */);
const Bar = sequelize.define("bar" /* ... */);
The model whose function we will be calling is called the source model, and the model which is passed as a parameter is called the target model.
Foo.hasOne(Bar, {
/* options */
});
This states that a One-to-One relationship exists between Foo and Bar with foreign key defined in Bar
Foo.belongsTo(Bar, {
/* options */
});
This states that a One-to-One or One-to-Many relationship exists between Foo and Bar with foreign key defined in Foo
Foo.hasMany(Bar, {
/* options */
});
This states that a One-to-Many relationship exists between Foo and Bar with foreign key defined in Bar
Foo.belongsToMany(Bar, {
// REQUIRED
through: "C", // Model can also be passed here
/* options */
});
This states that a Many-to-Many relationship exists between Foo and Bar through a junction table C
To setup a One-to-One relationship, we have to simply write
Foo.hasOne(Bar);
Bar.belongsTo(Foo);
In the above case, no option was passed. This will auto create a foreign key column in Bar referencing to the primary key of Foo. If the column name of PK of Foo is email, the column formed in Bar will be fooEmail.
The following options can be passed to customize the relation.
Foo.hasOne(Bar, {
foreignKey: "customNameForFKColumn", // Name for new column added to Bar
sourceKey: "email", // Column in Foo that FK will reference to
// The possible choices are RESTRICT, CASCADE, NO ACTION, SET DEFAULT and SET NULL
onDelete: "RESTRICT", // Default is SET NULL
onUpdate: "RESTRICT", // Default is CASCADE
});
Bar.belongsTo(Foo, {
foreignKey: "customNameForFKColumn", // Name for new column added to Bar
});
To setup a One-to-One relationship, we have to simply write
Foo.hasMany(Bar);
Bar.belongsTo(Foo);
In the above case, no option was passed. This will auto create a foreign key column in Bar referencing to the primary key of Foo. If the column name of PK of Foo is email, the column formed in Bar will be fooEmail.
The following options can be passed to customize the relation.
Foo.hasMany(Bar, {
foreignKey: "customNameForFKColumn", // Name for new column added to Bar
sourceKey: "email", // Column in Foo that FK will reference to
// The possible choices are RESTRICT, CASCADE, NO ACTION, SET DEFAULT and SET NULL
onDelete: "RESTRICT", // Default is SET NULL
onUpdate: "RESTRICT", // Default is CASCADE
});
Bar.belongsTo(Foo, {
foreignKey: "customNameForFKColumn", // Name for new column added to Bar
});
To setup a Many-to-Many relationship, we have to simply write
// This will create a new table rel referencing the PK(by default) of both the tables
Foo.belongsToMany(Bar, { through: "rel" });
Bar.belongsToMany(Foo, { through: "rel" });
The following options can be passed to customize the relation.
Foo.belongsToMany(Bar, {
as: "Bar",
through: "rel",
foreignKey: "customNameForFoo", // Custom name for column in rel referencing to Foo
sourceKey: "name", // Column in Foo which rel will reference to
});
Bar.belongsToMany(Foo, {
as: "Foo",
through: "rel",
foreignKey: "customNameForBar", // Custom name for column in rel referencing to Bar
sourceKey: "name", // Column in Foo which rel will reference to
});
There are two ways to create instances
We can use build method to create non-persistent(not saved to table) instances. They will automatically get the default values as stated while defining the Model.
To save to the table we need to save these instances explicitly.
const instance = ModelName.build({
firstColumn: "Lorem Ipsum",
secondColumn: "Dotor",
});
// To save this instance to the db
instance.save().then((savedInstance) => {});
We can create a method to create persistent(saved to table) instances
const instance = ModelName.create({
firstColumn: "Lorem Ipsum",
secondColumn: "Dotor",
});
There are two ways to update any instance
// Way 1
instance.secondColumn = "Updated Dotor";
instance.save().then(() => {});
// To update only some of the modified fields
instance.save({ fields: ["secondColumn"] }).then(() => {});
// Way 2
instance
.update({
secondColumn: "Updated Dotor",
})
.then(() => {});
// To update only some of the modified fields
instance
.update(
{
secondColumn: "Updated Dotor",
},
{ fields: ["secondColumn"] }
)
.then(() => {});
To delete/destroy any instance
instance.destroy().then(() => {});
Returns the row with the given value of Primary Key.
ModelName.findByPK(PKvalue).then((foundResult) => {});
Returns the first row with the given conditions.
ModelName.findOne({
// Optional options
// Filtering results using where
where: { firstColumn: "value" },
// Returning only specified columns
attributes: ["firstColumn", "secondColumn"],
}).then((foundResult) => {});
Returns the row found with given conditions. If no such row exists, creates one and returns that instead
ModelName.findOrCreate({
// Conditions that must be met
where: { firstColumn: "lorem ipsum" },
// Value of other columns to be set if no such row found
defaults: { secondColumn: "dotor" },
}).then(([result, created]) => {}); //Created is a bool which tells created or not
Returns all the rows satisfying the conditions
ModelName.findAll({
// Optional Options
where: {
firstColumn: "lorem ipsum",
},
offset: 10,
limit: 2,
}).then((results) => {});
Returns all the rows satisfying the conditions along with their count
ModelName.findAndCountAll({
where: {
firstColumn: "lorem ipsum",
},
}).then((results) => {
console.log(results.count);
console.log(results.rows);
});
Returns number of rows satisfying the conditions
ModelName.count({
where: {
firstColumn: "lorem ipsum",
},
}).then((c) => {});
Returns the value of the column with max value with given conditions
ModelName.max("age", {
where: {
firstColumn: "lorem ipsum",
},
}).then((maxAge) => {});
Returns the value of the column with min value with given conditions
ModelName.min("age", {
where: {
firstColumn: "lorem ipsum",
},
}).then((minAge) => {});
Returns the sum of all the values of the columns with given conditions
ModelName.sum({
where: {
firstColumn: "lorem ipsum",
},
}).then((sumAge) => {});
where can be used to filter the results we work on
We can directly pass the values
ModelName.findAll({
where: {
firstColumn: "lorem ipsum",
},
});
We can use AND and OR
const Op = Sequelize.Op;
ModelName.findAll({
where: {
[Op.and]: [{ secondColumn: 5 }, { thirdColumn: 6 }],
[Op.or]: [{ secondColumn: 5 }, { secondColumn: 6 }],
},
});
We can use various other operators
const Op = Sequelize.Op;
ModelName.findAll({
where: {
firstColumn: {
[Op.ne]: "lorem ipsum dotor", // Not equal to
},
},
});
We can mix and match too
const Op = Sequelize.Op;
ModelName.findAll({
where: {
[Op.or]: {
[Op.lt]: 1000,
[Op.eq]: null,
},
},
});
Here is the full list of Operators
const Op = Sequelize.Op
[Op.and]: [{a: 5}, {b: 6}] // (a = 5) AND (b = 6)
[Op.or]: [{a: 5}, {a: 6}] // (a = 5 OR a = 6)
[Op.gt]: 6, // > 6
[Op.gte]: 6, // >= 6
[Op.lt]: 10, // < 10
[Op.lte]: 10, // <= 10
[Op.ne]: 20, // != 20
[Op.eq]: 3, // = 3
[Op.is]: null // IS NULL
[Op.not]: true, // IS NOT TRUE
[Op.between]: [6, 10], // BETWEEN 6 AND 10
[Op.notBetween]: [11, 15], // NOT BETWEEN 11 AND 15
[Op.in]: [1, 2], // IN [1, 2]
[Op.notIn]: [1, 2], // NOT IN [1, 2]
[Op.like]: '%hat', // LIKE '%hat'
[Op.notLike]: '%hat' // NOT LIKE '%hat'
[Op.iLike]: '%hat' // ILIKE '%hat' (case insensitive) (PG only)
[Op.notILike]: '%hat' // NOT ILIKE '%hat' (PG only)
[Op.startsWith]: 'hat' // LIKE 'hat%'
[Op.endsWith]: 'hat' // LIKE '%hat'
[Op.substring]: 'hat' // LIKE '%hat%'
[Op.regexp]: '^[h|a|t]' // REGEXP/~ '^[h|a|t]' (MySQL/PG only)
[Op.notRegexp]: '^[h|a|t]' // NOT REGEXP/!~ '^[h|a|t]' (MySQL/PG only)
[Op.iRegexp]: '^[h|a|t]' // ~* '^[h|a|t]' (PG only)
[Op.notIRegexp]: '^[h|a|t]' // !~* '^[h|a|t]' (PG only)
[Op.like]: { [Op.any]: ['cat', 'hat']}
// LIKE ANY ARRAY['cat', 'hat'] - also works for iLike and notLike
[Op.overlap]: [1, 2] // && [1, 2] (PG array overlap operator)
[Op.contains]: [1, 2] // @> [1, 2] (PG array contains operator)
[Op.contained]: [1, 2] // <@ [1, 2] (PG array contained by operator)
[Op.any]: [2,3] // ANY ARRAY[2, 3]::INTEGER (PG only)
[Op.col]: 'user.organization_id' // = "user"."organization_id", with dialect specific column identifiers, PG in this example
[Op.gt]: { [Op.all]: literal('SELECT 1') }
// > ALL (SELECT 1)
[Op.contains]: 2 // @> '2'::integer (PG range contains element operator)
[Op.contains]: [1, 2] // @> [1, 2) (PG range contains range operator)
[Op.contained]: [1, 2] // <@ [1, 2) (PG range is contained by operator)
[Op.overlap]: [1, 2] // && [1, 2) (PG range overlap (have points in common) operator)
[Op.adjacent]: [1, 2] // -|- [1, 2) (PG range is adjacent to operator)
[Op.strictLeft]: [1, 2] // << [1, 2) (PG range strictly left of operator)
[Op.strictRight]: [1, 2] // >> [1, 2) (PG range strictly right of operator)
[Op.noExtendRight]: [1, 2] // &< [1, 2) (PG range does not extend to the right of operator)
[Op.noExtendLeft]: [1, 2] // &> [1, 2) (PG range does not extend to the left of operator)
ModelName.findAll({
order: [
["firstColumn", "DESC"],
["secondColumn", "ASC"],
],
});
For much more detailed information on ordering, check out the official docs
ModelName.findAll({
offset: 5, // Skip the first five results
limit: 5, // Return only five results
});
Send pull requests to add/modify to this post.
Code for this blog can be accessed here
Code for this blog can be accessed here
Markdown for this blog can be accessed here