MySQL數據庫的db.opt文件

MySQL的每個數據庫目錄中有一個文件db.opt,該文件主要 用來存儲當前數據庫的默認字符集和字符校驗規則。

eg.default-character-set=latin1
default-collation=latin1_swedish_ci

該文件中存儲的是創建數據庫時默認的字符集和字符集校驗規則，則該數據庫在以后創建表時如果沒有指定字符集和校驗規則，則該表的這兩個屬性將去自這兩個表。

MySQL源碼：

/* Set table default charset, if not set
SYNOPSIS
set_table_default_charset()
create_info Table create information
DESCRIPTION
If the table character set was not given explicitely,
let’s fetch the database default character set and
apply it to the table. */
static void set_table_default_charset(THD *thd,
HA_CREATE_INFO *create_info, char *db)
{
if (!create_info->default_table_charset)
{
HA_CREATE_INFO db_info;
load_db_opt_by_name(thd, db, &db_info);
create_info->default_table_charset= db_info.default_table_charset;
}
創建數據庫時指定字符集和字符集校驗規則：
create database if not exists test default [charset|character set ] utf8 default collate utf8_general_ci;
修改數據庫的字符集和字符集校驗規則：
alter database test default [charset|character set ] latin1 default collate latin1_swedish_ci;
創建數據庫create database
CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
[create_specification] …
create_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
也可以通過alter database修改
ALTER {DATABASE | SCHEMA} [db_name]
alter_specification …
alter_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name

MySQL源碼：

/* Set table default charset, if not set
SYNOPSIS
set_table_default_charset()
create_info Table create information
DESCRIPTION
If the table character set was not given explicitely,
let’s fetch the database default character set and
apply it to the table. */
static void set_table_default_charset(THD *thd,
HA_CREATE_INFO *create_info, char *db)
{
if (!create_info->default_table_charset)
{
HA_CREATE_INFO db_info;
load_db_opt_by_name(thd, db, &db_info);
create_info->default_table_charset= db_info.default_table_charset;
}
創建數據庫時指定字符集和字符集校驗規則：
create database if not exists test default [charset|character set ] utf8 default collate utf8_general_ci;
修改數據庫的字符集和字符集校驗規則：
alter database test default [charset|character set ] latin1 default collate latin1_swedish_ci;
創建數據庫create database
CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
[create_specification] …
create_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name
也可以通過alter database修改
ALTER {DATABASE | SCHEMA} [db_name]
alter_specification …
alter_specification:
[DEFAULT] CHARACTER SET [=] charset_name
| [DEFAULT] COLLATE [=] collation_name

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