Focus on the query operation of Golang xorm

Golang is an emerging programming language known for its efficiency, powerful concurrency capabilities and rapid development speed. Xorm is a powerful Golang ORM framework that allows developers to operate databases more conveniently.

In this article, we will focus on the query operation of Golang xorm and explore how to use xorm to achieve efficient data query. Before we begin, let's first understand what xorm is.

What is xorm?

xorm is an ORM framework based on Golang. It has the following two main features:

1. Mapping between database table fields and object attributes through structures and Tags, making Data operations are more convenient.
2. Supports rich query statements and realizes diversified query requirements.

After understanding the basic features of xorm, we will introduce the common query operations of xorm.

Common query operations

1. Querying a single object

In xorm, querying a single object is very convenient. Just use the ‘Get’ method, specify the target object type and query conditions. For example:

user := User{ID: 1}
has, err := engine.Get(&user)
if err != nil {
    log.Fatal(err)
}
if has {
    log.Println(user)
}

The above code will query the user information with ID 1. If the result is found, it will be stored in the user object.

2. Querying multiple objects

Querying multiple objects is very similar to querying a single object, except that you need to use the Find method and Slice object to store multiple results. For example:

type User struct {
    ID       int    `xorm:"'id' pk autoincr"`
    Name     string `xorm:"not null"`
    Password string `xorm:"not null"`
    Age      int
}
userList := make([]User)
err := engine.Find(&userList)
if err != nil {
    log.Fatal(err)
}
for _, user := range userList {
    log.Println(user)
}

The above code will query all user information in the User table and store the query results in the userList []User object. If the query results are found, the results are printed.

3. Conditional query

In xorm, conditional query is very flexible, and query conditions can be reasonably constructed for different query requirements.

For example, we can use the Where method to construct a simple query statement:

type User struct {
    ID       int    `xorm:"'id' pk autoincr"`
    Name     string `xorm:"not null"`
    Password string `xorm:"not null"`
    Age      int
}
userList := make([]User)
err := engine.Where("age > ?", 18).Find(&userList)
if err != nil {
    log.Fatal(err)
}
for _, user := range userList {
    log.Println(user)
}

The above code will query all users older than 18 years old in the User table, and store the query results in userList in this []User object.

In addition, xorm also supports more flexible query statement construction methods, such as:

type User struct {
    ID       int    `xorm:"'id' pk autoincr"`
    Name     string `xorm:"not null"`
    Password string `xorm:"not null"`
    Age      int
}
engine.Table("user").
    Join("left", "userinfo", "user.id = userinfo.user_id").
    Where("user.age > ?", 18).
    Or("userinfo.gender = ?", "male").
    Desc("user.age").
    Limit(10, 0).
    Find(&userList)
if err != nil {
    log.Fatal(err)
}
for _, user := range userList {
    log.Println(user)
}

The above code will query all users whose age is greater than 18 years old or whose gender is male. And sorted by age in descending order. Query the first 10 results and store the query results in the userList []User object.

The above is an introduction to the common query operations of xorm. In actual project development, we can flexibly use the query API provided by xorm to construct query statements that meet the actual needs of the project to achieve efficient and accurate data query.

Summary

As an efficient and powerful Golang ORM framework, xorm provides us with a rich query API that can help developers implement complex data query operations.

When using xorm for data query, we need to pay attention to some details. For example, xorm's query operation will perform ORM mapping by default, so if you need to query all fields, you need to define the corresponding Tag in the structure. In addition, xorm also supports fast and easy chained API calls, which allows us to construct complex query statements more conveniently and improve program development efficiency.

Finally, I hope that the introduction in this article can be helpful to Golang developers in database query.

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