Int -> varcher

将Int 转为varchar可以用 concat() 函数，比如 concat(8,’0′) 得到字符串 ’80′。

delete from core_channel;


drop procedure if exists insert_channel;

delimiter //

CREATE procedure insert_channel()
wholeblock:BEGIN
  declare str VARCHAR(255) default '';
  declare x INT default 0;
  SET x = 1;

  WHILE x <= 10 DO
    insert into core_channel (name) values (CONCAT("name",x));
    SET x = x + 1;
  END WHILE;

  select str;
END//

call insert_channel	();

...

Posted by Wei on 2020-01-31, Last Modified on 2025-04-23

Golang 命令

$ go
Go is a tool for managing Go source code.

Usage:

	go <command> [arguments]

The commands are:

	bug         start a bug report
	build       compile packages and dependencies
	clean       remove object files and cached files
	doc         show documentation for package or symbol
	env         print Go environment information
	fix         update packages to use new APIs
	fmt         gofmt (reformat) package sources
	generate    generate Go files by processing source
	get         add dependencies to current module and install them
	install     compile and install packages and dependencies
	list        list packages or modules
	mod         module maintenance
	run         compile and run Go program
	test        test packages
	tool        run specified go tool
	version     print Go version
	vet         report likely mistakes in packages

Use "go help <command>" for more information about a command.

Additional help topics:

	buildmode   build modes
	c           calling between Go and C
	cache       build and test caching
	environment environment variables
	filetype    file types
	go.mod      the go.mod file
	gopath      GOPATH environment variable
	gopath-get  legacy GOPATH go get
	goproxy     module proxy protocol
	importpath  import path syntax
	modules     modules, module versions, and more
	module-get  module-aware go get
	module-auth module authentication using go.sum
	module-private module configuration for non-public modules
	packages    package lists and patterns
	testflag    testing flags
	testfunc    testing functions

Use "go help <topic>" for more information about that topic.

...

Posted by Wei on 2020-01-30, Last Modified on 2025-04-23

Background

Although Go absorbs many features from all kinds of other languages, Go is mainly viewed as a C family language. One evidence is Go also supports pointers. Go pointers and C pointers are much similar in many aspects, but there are also some differences between Go pointers and C pointers. This article will list all kinds of concepts and details related to pointers in Go.

...

Posted by Wei on 2020-01-30, Last Modified on 2025-04-23

【Golang】类型转换 - 获取变量类型

如果某个函数的入参的类型是 interface{}，有下面几种方法可以获取入参的类型：

获取入参类型的方法

1 反射

import (
    "reflect"
    "fmt"
)
func main() {
    v := "hello world"
    fmt.Println(typeof(v))
}
func typeof(v interface{}) string {
    return reflect.TypeOf(v).String()
}

Example

其实，fmt.Sprintf("%T") 底层也是用反射实现的：

func (p *pp) printArg(arg interface{}, verb rune) {
	...
	// Special processing considerations.
	// %T (the value's type) and %p (its address) are special; we always do them first.
	switch verb {
	case 'T':
		p.fmt.fmtS(reflect.TypeOf(arg).String())
		return
  ...
  }
}

Usage:

import "fmt"
func main() {
    v := "hello world"
    fmt.Println(typeof(v))
}
func typeof(v interface{}) string {
    return fmt.Sprintf("%T", v)
}

...

Posted by Wei on 2020-01-30, Last Modified on 2025-04-23

【Linux】CentOS 安装Docker

卸载旧版本

较旧的 Docker 版本称为 docker 或 docker-engine 。如果已安装这些程序，请卸载它们以及相关的依赖项。

$ sudo yum remove docker \
         docker-client \
         docker-client-latest \
         docker-common \
         docker-latest \
         docker-latest-logrotate \
         docker-logrotate \
         docker-engine

...

Posted by Wei on 2020-01-30, Last Modified on 2025-04-23

西维蜀黍

【MySQL】MySQL 中的各种数据类型转换

Int -> varcher

【Golang】Golang 命令

Golang 命令

【Golang】指针（Pointers）

Background

【Golang】类型转换 - 获取变量类型

获取入参类型的方法

1 反射

Example

【Linux】CentOS 安装Docker

卸载旧版本

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