MySQL 二进制协议(protocol)准备响应

Question

正在编写一些使用 MySQL 二进制协议(protocol)与数据库通信的代码。

http://dev.mysql.com/doc/internals/en/client-server-protocol.html

我有一张 table :

CREATE TABLE People ( ID  INTEGER, Name VARCHAR(64), Age  SMALLINT, Sex  CHAR(1), Height DOUBLE);

当我发送COM_STMT_PREPARE时使用语句 “SELECT * FROM People where sex=? or Age=?” 发送到服务器。我得到一个COM_STMT_PREPARE_OK从服务器返回。

此包包含 2 个参数和 5 列，全部在 ColumnDefinition41 中定义。具有以下值的数据包:

PARAMETERS:
ColumnDefinition:
    catalog:                    def
    schema:                     <empty string>
    table:                      <empty string>
    orgTable:                   <empty string>
    name:                       ?
    orgName:                    <empty string>
    lengthOfFixedField:         12
    charSet:                    63
    columnLength:               0
    type:                       253(MYSQL_TYPE_VAR_STRING)
    flags:                      128
    decimal:                    0

ColumnDefinition:
    catalog:                    def
    schema:                     <empty string>
    table:                      <empty string>
    orgTable:                   <empty string>
    name:                       ?
    orgName:                    <empty string>
    lengthOfFixedField:         12
    charSet:                    63
    columnLength:               0
    type:                       253(MYSQL_TYPE_VAR_STRING)
    flags:                      128
    decimal:                    0


Columns:
ColumnDefinition:
    catalog:                    def
    schema:                     test
    table:                      People
    orgTable:                   people
    name:                       ID
    orgName:                    ID
    lengthOfFixedField:         12
    charSet:                    63
    columnLength:               11
    type:                       3(MYSQL_TYPE_LONG)
    flags:                      0
    decimal:                    0

ColumnDefinition:
    catalog:                    def
    schema:                     test
    table:                      People
    orgTable:                   people
    name:                       Name
    orgName:                    Name
    lengthOfFixedField:         12
    charSet:                    33
    columnLength:               192
    type:                       253(MYSQL_TYPE_VAR_STRING)
    flags:                      0
    decimal:                    0

ColumnDefinition:
    catalog:                    def
    schema:                     test
    table:                      People
    orgTable:                   people
    name:                       Age
    orgName:                    Age
    lengthOfFixedField:         12
    charSet:                    63
    columnLength:               6
    type:                       2(MYSQL_TYPE_SHORT)
    flags:                      0
    decimal:                    0

ColumnDefinition:
    catalog:                    def
    schema:                     test
    table:                      People
    orgTable:                   people
    name:                       Sex
    orgName:                    Sex
    lengthOfFixedField:         12
    charSet:                    33
    columnLength:               3
    type:                       254(MYSQL_TYPE_STRING)
    flags:                      0
    decimal:                    0

ColumnDefinition:
    catalog:                    def
    schema:                     test
    table:                      People
    orgTable:                   people
    name:                       Height
    orgName:                    Height
    lengthOfFixedField:         12
    charSet:                    63
    columnLength:               22
    type:                       5(MYSQL_TYPE_DOUBLE)
    flags:                      0
    decimal:                    31

第二个参数的类型为 MYSQL_TYPE_VAR_STRING，但我期望其类型为 MYSQL_TYPE_SHORT，因为它绑定(bind)到列 Age在具有此类型的表 People 中。

参数是否始终具有MYSQL_TYPE_VAR_STRING类型，或者是否有某种方法可以让服务器以我绑定(bind)的参数类型进行响应？

如果值得注意:

> mysql --help
mysql  Ver 14.14 Distrib 5.6.22, for osx10.10 (x86_64) using  EditLine wrapper
Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Answer 1

通过二进制协议(protocol)传递到 SQL Server 的参数始终编码为字符串。然后，SQL 服务器解析字符串并将它们在内部转换为正确的类型。