lua-resty-mysql是为基于cosocket API的ngx_lua提供的Lua Mysql客户端，通过它可以完成Mysql的操作。默认安装OpenResty时已经自带了该模块，使用文档可参考https://github.com/openresty/lua-resty-mysql。

1. 编辑mysql/test_mysql.lua

local function close_db( db )
  if not db then
    return
  end
  db:close()
end

local mysql = require("resty.mysql")
-- 创建实例
local db, err = mysql:new()
if not db then
  ngx.say("new  mysql error:", err)
  return
end
-- 设置超时时间(毫秒)
db:set_timeout(5000)

local props = {
  host = "172.19.237.44",
  port = 3306,
  database = "fuhuitest",
  user = "root",
  password = "wsy@123456"
}

local res, err, errno, sqlstate = db:connect(props)

if not res then
  ngx.say("connect to mysql error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
  return close_db(db)
end

-- 删除表
local drop_table_sql = "drop table if exists test"
res, err, errno, sqlstate = db:query(drop_table_sql)
if not res then
  ngx.say("drop table error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
  return close_db(db)
end

-- 创建表
local create_table_sql = "create table test(id int primary key auto_increment, ch varchar(100))"
res, err, errno, sqlstate = db:query(create_table_sql)
if not res then
   ngx.say("create table error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

-- 插入
local insert_sql = "insert into test (ch) values('hello')"
res, err, errno, sqlstate = db:query(insert_sql)
if not res then
   ngx.say("insert error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

res, err, errno, sqlstate = db:query(insert_sql)

ngx.say("insert rows : ", res.affected_rows, " , id : ", res.insert_id, "<br/>")

-- 更新
local update_sql = "update test set ch = 'hello2' where id =" .. res.insert_id
res, err, errno, sqlstate = db:query(update_sql)
if not res then
   ngx.say("update error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

ngx.say("update rows : ", res.affected_rows, "<br/>") 

-- 查询
local select_sql = "select id, ch from test"
res, err, errno, sqlstate = db:query(select_sql)
if not res then
   ngx.say("select error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

for i, row in ipairs(res) do
  for name, value in pairs(row) do
    ngx.say("select row ", i, " : ", name, " = ", value, "<br/>")
  end
end

ngx.say("<br/>")

--防止sql注入
local ch_param = ngx.req.get_uri_args()["ch"] or ''
--使用ngx.quote_sql_str防止sql注入
local query_sql = "select id, ch from test where ch = " .. ngx.quote_sql_str(ch_param)
res, err, errno, sqlstate = db:query(query_sql)
if not res then
   ngx.say("select error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

for i, row in ipairs(res) do
   for name, value in pairs(row) do
     ngx.say("select row ", i, " : ", name, " = ", value, "<br/>")
   end
end

-- 删除
local delete_sql = "delete from test"
res, err, errno, sqlstate = db:query(delete_sql)
if not res then
   ngx.say("delete error : ", err, " , errno : ", errno, " , sqlstate : ", sqlstate)
   return close_db(db)
end

ngx.say("delete rows : ", res.affected_rows, "<br/>")

close_db(db)

对于新增/修改/删除会返回如下格式的响应：

{
	insert_id = 0,
	server_status = 2,
	warning_count = 1,
	affected_rows = 32,
	message = nil
}

affected_rows表示操作影响的行数，insert_id是在使用自增序列时产生的id。
对于查询会返回如下格式的响应：

{
	{ id= 1, ch= "hello"},
	{ id= 2, ch= "hello2"}
}

null将返回ngx.null。

2. openResty.conf配置文件

    location /lua_mysql {
        default_type 'text/html';
        lua_code_cache on;
        content_by_lua_file /usr/openResty/lua/mysql/test_mysql.lua;
    }

3. 访问如http://127.0.0.1/lua_mysql?ch=hello进行测试，得到如下结果

insert rows : 1 , id : 2
update rows : 1
select row 1 : ch = hello
select row 1 : id = 1
select row 2 : ch = hello2
select row 2 : id = 2

select row 1 : ch = hello
select row 1 : id = 1
delete rows : 2

客户端目前还没有提供预编译SQL支持（即占位符替换位置变量），这样在入参时记得使用ngx.quote_sql_str进行字符串转义，防止sql注入；连接池和之前Redis客户端完全一样就不介绍了。


对于Mysql客户端的介绍基本够用了，更多请参考https://github.com/openresty/lua-resty-mysql。