Golang mysql operation introduction

Go (also known as Golang) is a statically strongly typed, compiled, concurrent programming language with garbage collection capabilities developed by Google. Below, I will introduce some operations about mysql from the go Getting Started Tutorial column.

go operates the mysql database. The library used is go-sql-driver/mysql. Install directly go get

go get -u github.com/go-sql-driver/mysql

sql.DB

The functions available for DB type are:

1. Query(c string, args interface{}…) (*Rows, error), commonly used in SELECT statements

2. Exec(c string, args interface{}…) (*Rows, error), commonly used with UPDATE and INSERT

3. Prepare(c string) (*Stmt, error), other statements, too It can be used to execute the above statement and return the Stmt pointer

sql.Stmt

Stmt is a prepared statement that can execute database statement operations. Commonly used functions are:

Exec(args interface{} …) (Result, error), given parameters and executes the prepared statement, and then returns the total result of the statement

//...
	stmt, err := db.Perpare("INSERT INTO User(user,pwd) VALUES (?, ?)")
	if err != nil {
		panic(err)
	}
	defer stmt.Close()
	_, err := stmt.Exec("laoli", "123456")
	if err != nil {
		panic(err)
	}
//...
//...
	stmt, err := db.Perpare("DELETE FROM User")
	if err != nil {
		panic(err)
	}
	defer stmt.Close()
	_, err := stmt.Exec()
	if err != nil {
		panic(err)
	}

Query(args interface{} …) ( *Rows, error), given parameters and executes the prepared statement, returning the row results, for example, the SELECT operation must be called with this function.

sql.Rows

Rows is the table returned by sql statement execution. Rows will occupy the cache. In Rows.Next(), if false is returned, it will be automatically released. cache.
Look at the source code:

// 源码
func (rs *Rows) Next() bool {
	var doClose, ok bool
	withLock(rs.closemu.RLocker(), func() {
		doClose, ok = rs.nextLocked()
	})
	if doClose {
		rs.Close() //在这里释放掉了
	}
	return ok
}

Example:

package main

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

var db *sql.DB
func mian() {
	db = sql.Open("mysql", "root:123456@tcp(127.0.0.1)/test")
	if err := db.Ping(); err != nil {
		panic(err)
	}
}

func Insert() {
	_, err := db.Exec("INSERT INTO User(user, pwd) VALUE (?, ?)", "laowang", "123456")
	if err != nil {
		panic(err)
	}
}

func SelectRow() {
	rows, err := db.Query("SELECT * FROM User WHERE user=?", "laowang")
	if err != nil {
		panic(err)
	}
	//defer rows.Close() //如果后面代码没有循环调用rows.Next()，就需要手动在这里释放一下，不然会一直占用缓存
	var user string
	var pwd string
	for rows.Next() {
		row.Scan(&user, &pwd)
	}
	print(user, pwd)
}

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