Node.js Sequelize Implement single instance field or bulk self-increment, self-subtraction _node.js

Self-increase and self-reduction of single instance

In Sequelize, an instance (Instance) represents a row of records in a database. There are two types of instance: a Non-persistent Model.build() instance created by, and a Model.create() persistent instance created by such methods. Whether it is a persistent or non-persistent instance, there is a increment() , decrement() two-person method, which is used for the increment of field values and for two operations.

1. instance.increment(fields, [options])-field value self-increasing
2. instance.decrement(fields, [options]) -field value self-minus
   

For example, find a user with ID 1 and increase its age by 1:

var User = Sequelize.import ('.. /lib/model/user/user ');
User.findbyid (1). Then (function (user) {
 user.increment (' age '). Then (function (user) {
 console.log (' Success ')})

increment()the SQL statements generated by the method are as follows:

UPDATE ' user ' SET ' age ' = ' age ' + 1 WHERE ' id ' = 1

increment()and decrement() The default of the self increase, the value of the self minus is 1. If you want to use a different value, you can specify it by the by parameter in option parameters [options].

For example, reducing the number of users to two fields by 2 can be done in the following ways:

User.increment ([' Age ', ' number '], {by:2}). Then (function (user) {
 console.log (' success ');
})

The generated SQL is as follows:

UPDATE ' user ' SET ' age ' = ' age ' + 2, ' number ' = ' number ' + 2 WHERE ' id ' = 1

The fields parameter can also be passed in by an object and specify the self increment, self decrement value. In this case, the options.by parameter is ignored.

For example, increase the number of users by 2 and age by 1:

User.increment ({age:-1, number:2}, {by:5}). Then (function (user) {
 console.log (' success ');
})

The generated SQL is as follows:

UPDATE ' user ' SET ' age ' = ' age ' +-1, ' number ' = ' number ' + 2 WHERE ' id ' = 1

Second, bulk self-increase, self-reduction

increment()And decrement() both are self increasing or self reducing operations on a single instance, that is, the data being manipulated is a row of data in the database. To achieve the following bulk self-increase, self-subtraction operation, you cannot use the instance operation:

UPDATE ' user ' SET ' age ' = ' age ' + 1 WHERE ' number ' > 10;

In Sequelize, the volume operation is usually achieved by model. But model does not increment() and decrement() method, can not be as convenient as instance or self reduction.

At this point, we can do this by using Model.update() the top-level methods in Sequelize sequelize.literal() :

sequelize.literal(val) -Create literal objects

sequelize.literal()method is used to create a literal object (val) that is passed directly into the generated SQL statement without any escaping.

For example, increase the age of 10 users by 1:

User.update ({sex:sequelize.literal (' age ' +1 ')}, {where:{number:{$gt:}}}). Then (function (user) {
 Console.log (' success ');
}

The resulting SQL statement is as follows:

UPDATE ' user ' SET ' age ' = ' age ' +1 WHERE ' number ' > 10

Summarize

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