一提字符集，可能有人会说，不管天崩地裂，全用utf8，整个世界都清净了。但某些字符集是需要更多CPU、消费更多的内存和磁盘空间、甚至影响索引使用，这还不包括令人蛋碎的乱码。可见、我们还是有必要花点时间略懂下MySQL字符集。
# 囊括三个层级：DB、Table、Column mysql> create database d charset utf8; Query OK, 1 row affected (0.04 sec) mysql> create table d.t -> (str varchar(10) charset latin1) -> default charset=utf8; Query OK, 0 rows affected (0.05 sec)

㈠ 显示字符集 

mysql> desc sakila.actor; +-------------+----------------------+------+-----+-------------------+-----------------------------+ | Field | Type | Null | Key | Default | Extra | +-------------+----------------------+------+-----+-------------------+-----------------------------+ | actor_id | smallint(5) unsigned | NO | PRI | NULL | auto_increment | | first_name | varchar(45) | NO | | NULL | | | last_name | varchar(45) | NO | MUL | NULL | | | last_update | timestamp | NO | | CURRENT_TIMESTAMP | on update CURRENT_TIMESTAMP | +-------------+----------------------+------+-----+-------------------+-----------------------------+ 4 rows in set (0.00 sec)

[root@DataHacker ~]# cat dbapi.py #!/usr/bin/env ipython #coding = utf-8 #Author: linwaterbin@gmail.com #Time: 2014-1-29 import MySQLdb as dbapi USER = 'root' PASSWD = 'oracle' HOST = '127.0.0.1' DB = 'sakila' conn = dbapi.connect(user=USER,passwd=PASSWD,host=HOST,db=DB)
[root@DataHacker ~]# ./show_charset.py --version 1.0

[root@DataHacker ~]# ./show_charset.py -h Usage: show_charset.py [options] <arg1> <arg2> [<arg3>...] Options: --version show program's version number and exit -h, --help show this help message and exit -d DB_NAME Database name(leave blank is all Databases) -t T_NAME Table name (leave blank is all tabless) -c C_NAME Column name(leave blank is all columns)

[root@DataHacker ~]# ./show_charset.py -d sakila -t actor sakila.actor.first_name: utf8 utf8_general_ci sakila.actor.last_name: utf8 utf8_general_ci

mysql> create table tt (str char(2) charset utf8); Query OK, 0 rows affected (0.20 sec) mysql> create table tt (str int(11) charset utf8); ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'charset utf8)' at line 1[root@DataHacker ~]# cat show_charset.py #!/usr/bin/env python from optparse import OptionParser from dbapi import conn import MySQLdb # 函数一：命令行参数输入 def parse_options(): parser = OptionParser(usage="%prog [options] <arg1> <arg2> [<arg3>...]",version='1.0',) parser.add_option("-d",dest="db_name",help="Database name(leave blank is all Databases)") parser.add_option("-t",dest="t_name",help="Table name (leave blank is all tabless)") parser.add_option("-c",dest="c_name",help="Column name(leave blank is all columns)") return parser.parse_args() # 主功能实现：显示字符集 def show_charsets(): query="""select * from information_schema.columns where table_schema not in ('mysql','INFORMATION_SCHEMA') and character_set_name is not null""" #三个if条件实现过滤 if options.db_name: query += " and table_schema='%s'" % options.db_name if options.t_name: query += " and table_name='%s'" % options.t_name if options.c_name: query += " and column_name='%s'" % options.c_name #默认返回值形式是元组，我们通过属性cursors.DictCursor转为字典 cur = conn.cursor(MySQLdb.cursors.DictCursor) cur.execute(query) for record in cur.fetchall(): character_set_name = record['CHARACTER_SET_NAME'] collation_name = record['COLLATION_NAME'] print "%s.%s.%s:\t%s\t%s" % (record['TABLE_SCHEMA'],record['TABLE_NAME'],record['COLUMN_NAME'],character_set_name,collation_name) cur.close() #采用try-finally形式关闭数据库连接 try: options,args = parse_options() show_charsets() finally: conn.close()

㈡ 修改列的字符集
[root@DataHacker ~]# ./modify.py -h Usage: modify.py schema_name.table_name.column_name new_charset_name [new_collate_name] Options: --version show program's version number and exit -h, --help show this help message and exit

#修改前 mysql> show create table testdb.t\G; *************************** 1. row *************************** Table: t Create Table: CREATE TABLE `t` ( `id` int(11) DEFAULT NULL, `name` varchar(10) CHARACTER SET latin1 DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8 1 row in set (0.00 sec) #修改 [root@DataHacker ~]# ./modify.py testdb.t.name gbk successfully executed: alter table testdb.t modify column name varchar(10) CHARSET gbk #修改后 mysql> show create table testdb.t\G; *************************** 1. row *************************** Table: t Create Table: CREATE TABLE `t` ( `id` int(11) DEFAULT NULL, `name` varchar(10) CHARACTER SET gbk DEFAULT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8 1 row in set (0.01 sec)
[root@DataHacker ~]# cat modify.py #!/usr/bin/env python import MySQLdb from dbapi import * from optparse import OptionParser #这里省略掉option值，只要求输入args def parse_options(): parser = OptionParser(usage="\n%prog schema_name.table_name.column_name new_charset_name [new_collate_name]",version='1.0',) return parser.parse_args() #主程序 def modify_column(): cur = conn.cursor(MySQLdb.cursors.DictCursor) v_sql = """ select * from information_schema.columns where table_schema='%s' and table_name='%s' and column_name='%s'""" % (schema_name,table_name,column_name) cur.execute(v_sql) row = cur.fetchone() #当row为null时，程序请求检查column是否存在 if not row: print "please check schema_name.table_name.column_name whether exists ?" exit(1) column_type = row['COLUMN_TYPE'] column_default = row['COLUMN_DEFAULT'] is_nullable = (row['IS_NULLABLE'] == 'YES') query = "alter table %s.%s modify column %s %s" % (schema_name,table_name,column_name,column_type) query += " CHARSET %s" % new_charset if collation_supplied: query += "COLLATE %s" % new_collation if not is_nullable: query += "NOT NULL" if column_default: query += "DEFAULT '%s'" % column_default try: alter_cur = conn.cursor() alter_cur.execute(query) print "successfully executed:\n \t%s" % query finally: alter_cur.close() cur.close() try: (options,args) = parse_options() if not 2<= len(args) <=3: print "Usage: schema_name.table_name.column_name new_charset_name [new_collate_name]" exit(1) column_tokens = args[0].split(".") if len(column_tokens) != 3: print "column must in the following format: schema_name.table_name.column_name" exit(1) schema_name,table_name,column_name = column_tokens new_charset = args[1] collation_supplied = (len(args) == 3) if collation_supplied: new_collation = args[2] modify_column() finally: if conn: conn.close()