Implementation method of golang paging query

Golang is a fast, safe, efficient and reliable language that is increasingly popular among developers. In practical applications, we often need to perform paging query of data. Golang also provides corresponding tools. This article will introduce the implementation method of paging query.

1. The concept of paging query

In the case of large data volume, querying all the data at one time will not only occupy more system resources, but also reduce the query speed. Therefore, We usually use paging query to query the data in batches. For example, if we want to query 10 pieces of data, we can set the amount of data on each page to 2. This will require 5 queries, 2 pieces of data at a time. After the query is completed, we will check the next page until all 10 pieces of data are complete. Check it out.

2. Implementation method

To implement paging query in Golang, we can use frameworks such as GORM or native SQL.

1. Use GORM to implement paging query

GORM is an ORM framework that provides a wealth of data operation methods, which greatly facilitates Golang database operations. In GORM, we can use the Limit and Offset methods to implement paging queries. The specific code is as follows:

import (
    "github.com/jinzhu/gorm"
    _ "github.com/jinzhu/gorm/dialects/mysql"
)

type User struct {
    gorm.Model
    Name string
    Age  int
}

func FindUsersByPage(pageNum int, pageSize int) ([]User, error) {
    var users []User
    db, err := gorm.Open("mysql", "user:password@/dbname?charset=utf8")
    if err != nil {
        return nil, err
    }
    defer db.Close()

    offset := (pageNum - 1) * pageSize
    db.Table("users").Offset(offset).Limit(pageSize).Find(&users)
    return users, nil
}

In the above code, we define a User structure to simulate the user table in the database; in the FindUsersByPage function, We used the Offset and Limit methods to perform paging query operations. Among them, offset represents the offset, pageSize represents the amount of data per page, and pageNum represents the number of pages currently queried.

2. Implement paging query with the help of native SQL

If we are accustomed to using native SQL statements for database operations, we can also implement paging query. The specific code is as follows:

import (
    "database/sql"
    _ "github.com/go-sql-driver/mysql"
)

type User struct {
    Id   int
    Name string
    Age  int
}

func FindUsersByPage(pageNum int, pageSize int) ([]User, error) {
    var users []User
    db, err := sql.Open("mysql", "user:password@/dbname?charset=utf8")
    if err != nil {
        return nil, err
    }
    defer db.Close()

    offset := (pageNum - 1) * pageSize
    rows, err := db.Query("SELECT id,name,age FROM users LIMIT ? OFFSET ?", pageSize, offset)
    if err != nil {
        return nil, err
    }
    defer rows.Close()

    for rows.Next() {
        var user User
        err := rows.Scan(&user.Id, &user.Name, &user.Age)
        if err != nil {
            return nil, err
        }
        users = append(users, user)
    }
    return users, nil
}

In the above code, we also define a User structure to simulate the user table in the database. In the FindUsersByPage function, we use the Query method to perform SQL queries, and also use offset and pageSize to determine the query range.

3. Summary

Through the above two methods, we can easily implement Golang’s paging query. Among them, GORM provides a simpler data operation method, while native SQL can more flexibly control the content and query method of query statements. For developers, they should choose based on their own needs and habits.

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