当前位置:网站首页>11-gorm-v2-03-basic query
11-gorm-v2-03-basic query
2022-07-05 06:15:00 【Operation and maintenance xuandegong】
List of articles
1. A simple example
Start with an example
- The table below
mysql> select * from xi_shu;
+----+------------+------+
| id | name | age |
+----+------------+------+
| 1 | LiuBei | 28 |
| 2 | GuanYu | 22 |
| 3 | ZhangFei | 20 |
+----+------------+------+
6 rows in set (0.00 sec)
- Code
package main
import (
"database/sql"
"fmt"
"gorm.io/driver/mysql"
"gorm.io/gorm"
"time"
)
type User struct {
ID int64
Age int64
Name string
}
func main() {
db,sqlDB,_ := connect()
defer sqlDB.Close()
var users []User
db.Find(&users)
fmt.Println(users)
}
func connect() (db *gorm.DB,sqlDB *sql.DB,err error) {
dsn := "root:[email protected](127.0.0.1:3306)/crow?charset=utf8&parseTime=True&loc=Local"
db, err = gorm.Open(mysql.Open(dsn), &gorm.Config{
})
sqlDB,_ = db.DB()
if err != nil {
fmt.Printf(err.Error())
defer sqlDB.Close()
}else {
fmt.Printf("OK\n")
sqlDB.SetMaxIdleConns(10)
sqlDB.SetMaxOpenConns(100)
sqlDB.SetConnMaxLifetime(time.Hour)
}
return
}
- The output is as follows
OK
[{
1 28 LiuBei} {
2 22 GuanYu} {
3 20 ZhangFei}]
2. The basic query
2.1 Get the first record , Sort by primary key
db.First(&user)
SELECT * FROM users ORDER BY id LIMIT 1;
2.2 Get a record , Do not specify sorting
db.Take(&user)
SELECT * FROM users LIMIT 1;
2.3 Get the last record , Sort by primary key
db.Last(&user)
SELECT * FROM users ORDER BY id DESC LIMIT 1;
2.4 Get all the records
db.Find(&users)
SELECT * FROM users;
2.5 Query through the primary key ( Only applicable if the primary key is numeric )
db.First(&user, 2)
SELECT * FROM users WHERE id = 10;
2.6 Query the specified field
db.Select("name,age").Find(&users)
- Example
func main() {
db,_ := connect()
defer db.Close()
var users []xiShu
db.Select("name,age").Find(&users)
fmt.Println(user)
}
- Example ( Using slices )
db.Select([]string{
"name", "age"}).Find(&users)
3. where
3.1 Native sql
3.1.1 Easy to use
- grammar
db.Where("name = ?", "LiuBei").First(&users)
SELECT * FROM users WHERE name = 'LiuBei' limit 1;
- Example 1
"1. A simple example " in main The function is replaced as follows :
func main() {
db,sqlDB,_ := connect()
defer sqlDB.Close()
var users []User
db.Where("name = ?", "LiuBei").First(&users)
fmt.Println(users)
db.Where("name = ?", "GuanYu").First(&users)
fmt.Println(users)
}
Query results :
OK
&[{
1 LiuBei 28}]
&[{
2 GuanYu 22}]
- Example 2
If continuous query uses structure to receive data
func main() {
db,sqlDB,_ := connect()
defer sqlDB.Close()
var user User
db.Where("name = ?", "LiuBei").First(&user)
fmt.Println(user)
db.Where("name = ?", "GuanYu").First(&user)
fmt.Println(user)
}
Output is
OK
{
1 28 LiuBei}
2022/02/11 23:54:54 /data/goproject/src/crow-gorm/main.go:29 record not found
[0.796ms] [rows:0] SELECT * FROM `users` WHERE name = 'GuanYu' AND `users`.`id` = 1 ORDER BY `users`.`id` LIMIT 1
{
1 28 LiuBei}
Error reporting is visible "WHERE name = ‘GuanYu’ AND `users`.`id` = 1 ", Explain that the results of the first query will be brought to the second query
Tried it on , If the structure data is cleared before the second query , You can query for the second time
func main() {
db,sqlDB,_ := connect()
defer sqlDB.Close()
var user User
db.Where("name = ?", "LiuBei").First(&user)
fmt.Println(user)
user = User{
} // eliminate user
db.Where("name = ?", "GuanYu").First(&user)
fmt.Println(user)
}
3.1.2 <> ( Not for )
db.Where("name <> ?", "LiuBei").Find(&users)
3.1.3 IN
db.Where("name in (?)", []string{
"CaoCao","LiuBei","SunQuan"}).Find(&users)
3.1.4 LIKE
db.Where("name LIKE ?", "%Liu%").Find(&users)
3.1.5 AND
db.Where("name = ? AND Age > ? ", "LiuBei",20).Find(&users)
3.1.6 BETWEEN
db.Where("created_at BETWEEN ? AND ?", lastWeek, today).Find(&users)
3.1.7 Time
db.Where("updated_at < ?", currentTime).Find(&users)
3.2 adopt go Object query for
3.2.1 adopt Struct Inquire about
- grammar
db.Where(STRUCT_NAME).First(&users)
- Example
func main() {
db,sqlDB,_ := connect()
defer sqlDB.Close()
user := User {
Name: "GuanYu",
Age: 22,
}
db.Where(user).First(&user)
fmt.Println(user)
}
3.2.2 adopt Map Inquire about
db.Where(map[string]interface{
}{
"name": "GuanYu", "age": 22}).Find(&users)
3.2.3 Pay attention to problems
- The value is
0
、''
、false
This field will not be used to build query conditions
func main() {
db,_ := connect()
defer db.Close()
var users []User
result := db.Where(map[string]interface{
}{
"name": 0, "age": 20}).Find(&users)
fmt.Println(users)
}
result
OK
[{
3 ZhangFei 20} {
5 ZhuGeLiang 20} {
6 MaChao 20}]
so ,name The value of is 0,ID Empty will not , Do not write sql sentence .
4. Not
and WHERE similar , Don't start the story
- Get the first record after filtering , Sort by primary key
db.Not("name", "LiuBei").First(&user)
SELECT * FROM users WHERE name <> "LiuBei" LIMIT 1;
- Using arrays / Slice filter
db.Not("name", []string{
"CaoCao", "LiuBei","SunQuan"}).Find(&users)
SELECT * FROM users WHERE name NOT IN ("CaoCao", "LiuBei","SunQuan");
- Not in primary key slice in
db.Not([]int64{
1,2,3}).First(&user)
SELECT * FROM users WHERE id NOT IN (1,2,3);
Example
func main() {
db,_ := connect()
defer db.Close()
var users []User
result := db.Not([]int64{
1,2,3}).Find(&users)
fmt.Println(users)
}
result
[{
4 ZhaoYun 18} {
5 ZhuGeLiang 20} {
6 MaChao 20}]
As you can see above ,ID yes 1.2.3 That's filtered
- Native SQL
db.Not("name = ?", "LiuBei").First(&user)
SELECT * FROM users WHERE NOT(name = "LiuBei");
- Struct/Map
db.Not(map[string]interface{
}{
"name": "LiuBei", "age": 20}).Find(&users)
SELECT * FROM users WHERE name <> "LiuBei";
5. Or
Connect two conditions , The two sides can be written in different ways , If one side is primitive sql On one side is the structure :
db.Where("name = ?", "LiuBei").Or(xiShu{
Name: "GuanYu"}).Find(&users)
6. Intra line condition query
- Non numeric primary key query
db.First(&user, 2)
SELECT * FROM users WHERE id = 23 LIMIT 1;
Example
func main() {
db,_ := connect()
defer db.Close()
var users []User
result := db.First(&users, 2)
fmt.Println(users)
}
- Primary key query ( Numbers / Non digital )
db.First(&user, "id = ?", "xxxx")
SELECT * FROM users WHERE id = 'xxxxx' LIMIT 1;
- Native SQL
db.Find(&users, "name = ?", "LiuBei")
SELECT * FROM users WHERE name = "LiuBei";
db.Find(&users, "name <> ? AND age > ?", "LiuBei", 20)
SELECT * FROM users WHERE name <> "LiuBei" AND age > 20;
- Struct
db.Find(&users, User{
Age: 20})
SELECT * FROM users WHERE age = 20;
- Map
db.Find(&users, map[string]interface{
}{
"age": 20})
SELECT * FROM users WHERE age = 20;
边栏推荐
- 2022年貴州省職業院校技能大賽中職組網絡安全賽項規程
- Leetcode heap correlation
- Network security skills competition in Secondary Vocational Schools -- a tutorial article on middleware penetration testing in Guangxi regional competition
- LeetCode 0107.二叉树的层序遍历II - 另一种方法
- Leetcode-556: the next larger element III
- How to adjust bugs in general projects ----- take you through the whole process by hand
- Leetcode-22: bracket generation
- In depth analysis of for (VaR I = 0; I < 5; i++) {settimeout (() => console.log (I), 1000)}
- Leetcode-9: palindromes
- 多屏电脑截屏会把多屏连着截下来,而不是只截当前屏
猜你喜欢
Appium自动化测试基础 — Appium测试环境搭建总结
1.15 - input and output system
SPI 详解
Some common problems in the assessment of network engineers: WLAN, BGP, switch
1.15 - 输入输出系统
传统数据库逐渐“难适应”,云原生数据库脱颖而出
Groupbykey() and reducebykey() and combinebykey() in spark
Introduction to LVS [unfinished (semi-finished products)]
中职网络安全技能竞赛——广西区赛中间件渗透测试教程文章
SQLMAP使用教程(二)实战技巧一
随机推荐
One question per day 1765 The highest point in the map
QQ computer version cancels escape character input expression
Introduction to LVS [unfinished (semi-finished products)]
1.15 - 输入输出系统
One question per day 2047 Number of valid words in the sentence
Matrixdb V4.5.0 was launched with a new mars2 storage engine!
QQ电脑版取消转义符输入表情
MatrixDB v4.5.0 重磅发布,全新推出 MARS2 存储引擎!
[practical skills] technical management of managers with non-technical background
【Rust 笔记】17-并发(下)
leetcode-31:下一个排列
【Rust 笔记】14-集合(上)
Data visualization chart summary (I)
1040 Longest Symmetric String
JS quickly converts JSON data into URL parameters
Introduction and experience of wazuh open source host security solution
Quickly use Amazon memorydb and build your own redis memory database
One question per day 1447 Simplest fraction
R language [import and export of dataset]
Leetcode dynamic programming