erlang连接mysql数据库后为什么fetch说匹配不到这个函数

Question

小弟今天在连接mysql数据库。连接上了数据库之后怎么查询会报这个错。求解!

mysql:fetch(p1,<<"SELECT * FROM SERVICE">>).
** exception error: no function clause matching
mysql:fetch(p1,<<"SELECT * FROM SERVICE">>)

Answer 1

需要注意，官方放在googlecode的测试代码已经旧了，fetch接口实际上需要一个二进制list，所以是[<<"select * from table">>]格式，而不是<<”select * from table”>>格式。

以下是增、删、改、查操作的测试代码：
[code="java"]
-module(mysql_test).
-export([start/0]).

start () ->

% 连接数据库
mysql:start_link(conn1, "localhost", "root", "ybybyb", "webgame"),

% 插入数据
Result1 = mysql:fetch(
    conn1,
    [<<
    "INSERT INTO"
    "        `player`"
    "    SET"
    "        `username`         = 'test',"
    "        `joined_datetime`  = now(),"
    "        `logined_datetime` = now();"
    >>]
),

io:format("Result1: ~p~n", [Result1]),

% 查询数据
Result2 = mysql:fetch(conn1, [<<"SELECT * FROM player">>]),

io:format("Result2: ~p~n", [Result2]),

% 更新数据
Result3 = mysql:fetch(
    conn1,
    [<<
    "UPDATE"
    "    `player`"
    "SET"
    "    `username` = 'test_player'"
    "where"
    "    `username` = 'test'"
    >>]
),

io:format("Result3: ~p~n", [Result3]),

% 查询数据
Result4 = mysql:fetch(conn1, [<<"SELECT * FROM player">>]),

io:format("Result4: ~p~n", [Result4]),

% 删除数据
Result5 = mysql:fetch(
    conn1,
    [<<
    "DELETE FROM `player` WHERE `username` = 'test_player'"
    >>]
),

io:format("Result5: ~p~n", [Result5]),

% 查询数据
Result6 = mysql:fetch(conn1, [<<"SELECT * FROM player">>]),

io:format("Result4: ~p~n", [Result6]),

ok.

[/code]