导入对应的包
// 安装
$ go get github.com/go-sql-driver/mysql
// 导入
import (
"database/sql"
_ "thirdpkg/go-sql-driver/mysql"
)
初始化mysql客户端
// 打开数据库,格式是⽤户名:密码@协议/数据库名称？编码⽅式
db, err := sql.Open("mysql", "root:123456@tcp(127.0.0.1:3306)/test?charset=utf8"
if err != nil {
fmt.Println(err)
}
// 确保db正常关闭
defer db.Close()
// 使用前Ping, 确保db连接正常
err = db.Ping()
if err != nil {
fmt.Println(err)
}
数据库查询示例
golang本身的mysql库存在很多不便利的地方和一些坑，需要注意一下
// 假设日期和查询条件是从http客户端发过来的参数
// start_day: "2020-05-02"
// end_day: "2020-05-10"
// city: "[1,2,3,4,5,6]"
// 1) 获取参数并校验参数有效性
var citys []int
r.FormValue("city")
startDay := r.FormValue("start_day")
endDay := r.FormValue("end_day")
err = json.Unmarshal([]byte(cityStr), &citys)
if err != nil {
fmt.Println(err)
}
if ok, _ := regexp.MatchString(`^\d{4}-\d{2}-\d{2}$`, startDay); !ok {
fmt.Printf("invalid param, start day:[%s]\n", startDay)
}
if ok, _ := regexp.MatchString(`^\d{4}-\d{2}-\d{2}$`, endDay); !ok {
fmt.Printf("invalid param, end day:[%s]\n", endDay)
}
// 2) 构造sql语句
sqlText := `
select
sum(sales)/(to_days('end_day') - to_days('start_day')) as daily_sum,
sum(price)/(to_days('end_day') - to_days('start_day')) as daily_price
from sales_table
where dt between 'start_day' and 'end_day'
and city_id in %s
`
// 获取城市对应的range字符串用于sql语句："[1,2,3,4,5,6]" ==> "(1,2,3,4,5,6)"
cityRange := genSQLRangeStrByIntArr(citys)
// 通过fmt.Sprintf拼接得到对应的字符串
sqlText = fmt.Sprintf(sqlText, cityRange)
// 对于多次出现的变量, 使用strings.Replace替换
sqlText = strings.Replace(sqlText, "start_day", startDay, -1)
sqlText = strings.Replace(sqlText, "endDay", endDay, -1)
// 3) 查询sql
rows, err := db.Query(sqlText)
defer rows.Close() // rows必须scan, 否则会导致链接无法关闭而一直占用链接, 直到超过设置的生命周期
if err != nil {
fmt.Println(err)
}
// 存储结果的切片, 用于存储多行返回结果
var resInfoArr []*resInfo
for rows.Next() {
var tempInfo resInfo
// 注意rows.Scan的参数顺序和个数都很重要, 必须和sql查询语句的返回结果一一对应
// 另外必须注意结构体的变量类型也必须和mysql一致
rows.Scan(&resInfo.dailySum, &resInfo.dailyPrict)
resInfoArr = append(resInfoArr, &tempInfo)
}
// 存储结果的结构体
type resInfo struct {
dailySum float64 `db:"daily_sum"`
dailyPrict float63 `db:"daily_price"`
}
// 生成between...and...的范围字符串, 用于SQL语句
func genSQLRangeStrByIntArr(arr []int) (res string) {
var tempStrArr = make([]string, len(arr))
for k, v := range arr {
tempStrArr[k] = fmt.Sprintf("%d", v)
}
res = "(" + strings.Join(tempStrArr, ",") + ")"
return
}
其他操作示例
import (
_"mysql"
"database/sql"
"fmt"
)
func check(err error){
if err!=nil{
fmt.Println(err)
}
}
func main(){
db,err:=sql.Open("mysql","root:123456@tcp(127.0.0.1:3306)/employee")
check(err)
//query
type info struct {
id int `db:"id"`
name string `db:"name"`
age int `db:"age"`
sex string `db:"sex"`
salary int `db:"salary"`
work string `db:"work"`
inparty string `db:"inparty"`
}
rows,err:=db.Query("SELECT * FROM message")
check(err)
for rows.Next(){
var s info
err=rows.Scan(&s.id,&s.name,&s.age,&s.sex,&s.salary,&s.work,&s.inparty,)
check(err)
fmt.Println(s)
}
rows.Close()
//insert
db.Exec("INSERT INTO message(id,name,age,sex,salary,work,inparty)VALUES (?,?,?,?,?,?,?)",7,"李白",80,"男",1000,"中","是")
//update
results,err:=db.Exec("UPDATE message SET salary=? where id=?",8900,3)
check(err)
fmt.Println(results.RowsAffected())
//delete
results,err:=db.Exec("DELETE FROM message where id=?",2)
check(err)
fmt.Println(results.RowsAffected())
第三方库: gendry
以我们上面的查询为例，
golang本身的go-sql-driver/mysql本身编程和维护方便都有不少需要注意的问题，Gendry是一个用于辅助操作数据库的Go包，提供了一系列的方法来为你调用标准库database/sql中的方法准备参数。
主要包括三部分：manager、builder和scanner
详细的资料可以阅读各个库的README：
-
manager：https://github.com/didi/gendry/tree/master/manager -
scanner：https://github.com/didi/gendry/tree/master/scanner -
builder：https://github.com/didi/gendry/tree/master/builder
1. manager
主要用于初始化连接池，即sql.DB对象，设置各种参数：
var db *sql.DB
var err error
db, err = manager
.New(dbName, user, password, host)
.Set(
manager.SetCharset("utf8"),
manager.SetAllowCleartextPasswords(true),
manager.SetInterpolateParams(true),
manager.SetTimeout(1 * time.Second),
manager.SetReadTimeout(1 * time.Second)
).Port(3302).Open(true)
manager本质做的事情即生成dataSourceName，一般它的格式如下：
[username[:password]@][protocol[(address)]]/dbname[?param1=value1&...¶mN=valueN]
2. Builder
Builder用于生成sql语句，手写sql简单直观但是可维护性差，并且硬编码容易出错，如果遇到大where in查询，且in的集合内容又是动态的就很麻烦了。
where := map[string]interface{}{
"city in": []string{"beijing", "shanghai"},
"score": 5,
"age >": 35,
"address": builder.IsNotNull,
"_orderby": "bonus desc",
"_groupby": "department",
}
table := "some_table"
selectFields := []string{"name", "age", "sex"}
cond, values, err := builder.BuildSelect(table, where, selectFields)
//cond = SELECT name,age,sex FROM g_xxx WHERE (score=? AND city IN (?,?) AND age>? AND address IS NOT NULL) GROUP BY department ORDER BY bonus DESC
//values = []interface{}{"beijing", "shanghai", 5, 35}
rows,err := db.Query(cond, values...)
如果你想清除where map中的零值可以使用builder.OmitEmpty：
where := map[string]interface{}{
"score": 0,
"age": 35,
}
finalWhere := builder.OmitEmpty(where, []string{"score", "age"})
// finalWhere = map[string]interface{}{"age": 35}
// support: Bool, Array, String, Float32, Float64, Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr, Map, Slice, Interface, Struct
同时，builder还提供一个便捷方法来进行聚合查询，比如：count,sum,max,min,avg：
where := map[string]interface{}{
"score > ": 100,
"city in": []interface{}{"Beijing", "Shijiazhuang",}
}
// AggregateSum,AggregateMax,AggregateMin,AggregateCount,AggregateAvg is supported
result, err := AggregateQuery(ctx, db, "tableName", where, AggregateSum("age"))
sumAge := result.Int64()
result,err = AggregateQuery(ctx, db, "tableName", where, AggregateCount("*"))
numberOfRecords := result.Int64()
result,err = AggregateQuery(ctx, db, "tableName", where, AggregateAvg("score"))
averageScore := result.Float64()
对于比较复杂的查询, NamedQuery将会派上用场:
cond, vals, err := builder.NamedQuery("select * from tb where name={{name}} and id in (select uid from anothertable where score in {{m_score}})", map[string]interface{}{
"name": "caibirdme",
"m_score": []float64{3.0, 5.8, 7.9},
})
assert.Equal("select * from tb where name=? and id in (select uid from anothertable where score in (?,?,?))", cond)
assert.Equal([]interface{}{"caibirdme", 3.0, 5.8, 7.9}, vals)
3. Scanner
执行了数据库操作之后，要把返回的结果集和自定义的struct进行映射。Scanner提供一个简单的接口通过反射来进行结果集和自定义类型的绑定：
type Person struct {
Name string `ddb:"name"`
Age int `ddb:"m_age"`
}
rows,err := db.Query("SELECT age as m_age,name from g_xxx where xxx")
defer rows.Close()
var students []Person
scanner.Scan(rows, &students)
for _,student := range students {
fmt.Println(student)
}
scanner进行反射时会使用结构体的tag，如上所示，scanner会把结果集中的 m_age绑定到结构体的Age域上。默认使用的tagName是ddb:"xxx"，你也可以自定义：
scanner.SetTagName("json")
type Person struct {
Name string `json:"name"`
Age int `json:"m_age"`
}
// ...
var student Person
scaner.Scan(rows, &student)
scaner.SetTagName是全局设置，为了避免歧义，只允许设置一次，一般在初始化DB阶段进行此项设置
4. ScanMap
ScanMap方法返回的是一个map，有时候你可能不太像定义一个结构体去存你的中间结果，那么ScanMap或许比较有帮助：
rows,_ := db.Query("select name,m_age from person")
result,err := scanner.ScanMap(rows)
for _,record := range result {
fmt.Println(record["name"], record["m_age"])
}
需要注意的点：
- 如果是使用
Scan或者ScanMap的话，你必须在之后手动close rows - 传给
Scan的必须是引用 -
ScanClose和ScanMapClose不需要手动close rows
5. CLI Tool
除了以上API，Gendry还提供了一个命令行工具来进行代码生成，既可以生成Gendry相关的golang结构体，也可以生成完整的数据层dao layer：
https://github.com/caibirdme/gforge
- 安装
go get -u github.com/caibirdme/gforge
- 用法
##################################################################
# 帮助文档
##################################################################
> gforge -h
A collection of tools to generate code for operating database supported by Gendry
Options:
-h, --help display help information
-v version
Commands:
help display help information
table schema could generate go struct code for given table
dao dao generates code of dao layer by given table name
##################################################################
# 生成表格对应的结构体
##################################################################
> gforge help table
schema could generate go struct code for given table
Options:
-d database name
-t table name
-u user name
-p password
-h[=localhost] host
-P[=3306] port
> gforge table -uusername -ppassword -hip -dinformation_schema -tCOLUMNS
// COLUMNS is a mapping object for COLUMNS
type COLUMNS struct {
TABLECATALOG string `json:"TABLE_CATALOG"
TABLESCHEMA string `json:"TABLE_SCHEMA"
TABLENAME string `json:"TABLE_NAME"
COLUMNNAME string `json:"COLUMN_NAME"
ORDINALPOSITION uint64 `json:"ORDINAL_POSITION"
COLUMNDEFAULT string `json:"COLUMN_DEFAULT"
ISNULLABLE string `json:"IS_NULLABLE"
DATATYPE string `json:"DATA_TYPE"
CHARACTERMAXIMUMLENGTH uint64 `json:"CHARACTER_MAXIMUM_LENGTH"
CHARACTEROCTETLENGTH uint64 `json:"CHARACTER_OCTET_LENGTH"
NUMERICPRECISION uint64 `json:"NUMERIC_PRECISION"
NUMERICSCALE uint64 `json:"NUMERIC_SCALE"
DATETIMEPRECISION uint64 `json:"DATETIME_PRECISION"
CHARACTERSETNAME string `json:"CHARACTER_SET_NAME"
COLLATIONNAME string `json:"COLLATION_NAME"
COLUMNTYPE string `json:"COLUMN_TYPE"
COLUMNKEY string `json:"COLUMN_KEY"
EXTRA string `json:"EXTRA"
PRIVILEGES string `json:"PRIVILEGES"
COLUMNCOMMENT string `json:"COLUMN_COMMENT"
GENERATIONEXPRESSION string `json:"GENERATION_EXPRESSION"
}
##################################################################
# 根据一张表生成对应的dao layer
##################################################################
> gforge dao -uusername -ppassword -hip -dinformation_schema -tCOLUMNS | gofmt
package COLUMNS
import (
"database/sql"
"errors"
"github.com/didichuxing/gendry/builder"
"github.com/didichuxing/gendry/scanner"
)
/*
This code is generated by ddtool
*/
// COLUMNS is a mapping object for COLUMNS
type COLUMNS struct {
TABLECATALOG string `json:"TABLE_CATALOG"`
TABLESCHEMA string `json:"TABLE_SCHEMA"`
TABLENAME string `json:"TABLE_NAME"`
COLUMNNAME string `json:"COLUMN_NAME"`
ORDINALPOSITION uint64 `json:"ORDINAL_POSITION"`
COLUMNDEFAULT string `json:"COLUMN_DEFAULT"`
ISNULLABLE string `json:"IS_NULLABLE"`
DATATYPE string `json:"DATA_TYPE"`
CHARACTERMAXIMUMLENGTH uint64 `json:"CHARACTER_MAXIMUM_LENGTH"`
CHARACTEROCTETLENGTH uint64 `json:"CHARACTER_OCTET_LENGTH"`
NUMERICPRECISION uint64 `json:"NUMERIC_PRECISION"`
NUMERICSCALE uint64 `json:"NUMERIC_SCALE"`
DATETIMEPRECISION uint64 `json:"DATETIME_PRECISION"`
CHARACTERSETNAME string `json:"CHARACTER_SET_NAME"`
COLLATIONNAME string `json:"COLLATION_NAME"`
COLUMNTYPE string `json:"COLUMN_TYPE"`
COLUMNKEY string `json:"COLUMN_KEY"`
EXTRA string `json:"EXTRA"`
PRIVILEGES string `json:"PRIVILEGES"`
COLUMNCOMMENT string `json:"COLUMN_COMMENT"`
GENERATIONEXPRESSION string `json:"GENERATION_EXPRESSION"`
}
//GetOne gets one record from table COLUMNS by condition "where"
func GetOne(db *sql.DB, where map[string]interface{}) (*COLUMNS, error) {
if nil == db {
return nil, errors.New("sql.DB object couldn't be nil")
}
cond, vals, err := builder.BuildSelect("COLUMNS", where, nil)
if nil != err {
return nil, err
}
row, err := db.Query(cond, vals...)
if nil != err || nil == row {
return nil, err
}
defer row.Close()
var res *COLUMNS
err = scanner.Scan(row, &res)
return res, err
}
//GetMulti gets multiple records from table COLUMNS by condition "where"
func GetMulti(db *sql.DB, where map[string]interface{}) ([]*COLUMNS, error) {
if nil == db {
return nil, errors.New("sql.DB object couldn't be nil")
}
cond, vals, err := builder.BuildSelect("COLUMNS", where, nil)
if nil != err {
return nil, err
}
row, err := db.Query(cond, vals...)
if nil != err || nil == row {
return nil, err
}
defer row.Close()
var res []*COLUMNS
err = scanner.Scan(row, &res)
return res, err
}
//Insert inserts an array of data into table COLUMNS
func Insert(db *sql.DB, data []map[string]interface{}) (int64, error) {
if nil == db {
return nil, errors.New("sql.DB object couldn't be nil")
}
cond, vals, err := builder.BuildInsert("COLUMNS", data)
if nil != err {
return 0, err
}
result, err := db.Exec(cond, vals...)
if nil != err || nil == result {
return 0, err
}
return result.LastInsertId()
}
//Update updates the table COLUMNS
func Update(db *sql.DB, where, data map[string]interface{}) (int64, error) {
if nil == db {
return 0, errors.New("sql.DB object couldn't be nil")
}
cond, vals, err := builder.BuildUpdate("COLUMNS", where, data)
if nil != err {
return 0, err
}
result, err := db.Exec(cond, vals...)
if nil != err {
return 0, err
}
return result.RowsAffected()
}
// Delete deletes matched records in COLUMNS
func Delete(db *sql.DB, where,data map[string]interface{}) (int64, error) {
if nil == db {
return 0, errors.New("sql.DB object couldn't be nil")
}
cond,vals,err := builder.BuildDelete("{{.TableName}}", where)
if nil != err {
return 0, err
}
result,err := db.Exec(cond, vals...)
if nil != err {
return 0, err
}
return result.RowsAffected()
}
其他文章
[Go基础]Json在Go中的使用
[Go基础]理解 Go 标准库中的 atomic.Value 类型
[Golang实战]thread pool的go实现
Reference
[1] https://www.runoob.com/mysql/mysql-install.html
[2] https://www.jianshu.com/p/af27b7a2a239
[3] https://blog.csdn.net/a670531899/article/details/81226752
[4] https://github.com/didi/gendry