MySQL数据库设计之利用Python操作Schema方法详解

mysql> use sakila; 
mysql> desc 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 ~]# cat QueryColumnMetaData.py 
#!/usr/bin/env ipython 
 
from dbapi import * 
 
cur = conn.cursor() 
statement = """select * from actor limit 1""" 
cur.execute(statement) 
 
print "output column metadata....." 
print 
for record in cur.description: 
  print record 
 
cur.close() 
conn.close() 

[root@DataHacker ~]# chmod +x QueryColumnMetaData.py 
[root@DataHacker ~]# ./QueryColumnMetaData.py 
output column metadata..... 
 
('actor_id', 2, 1, 5, 5, 0, 0) 
('first_name', 253, 8, 45, 45, 0, 0) 
('last_name', 253, 7, 45, 45, 0, 0) 
('last_update', 7, 19, 19, 19, 0, 0) 

In [1]: from dbapi import * 
In [2]: cur = conn.cursor() 
In [3]: v_sql = "select actor_id,last_name from actor limit 2" 
In [4]: cur.execute(v_sql) 
Out[4]: 2L 
In [5]: results = cur.fetchone() 
In [6]: print results[0] 
58 
In [7]: print results[1] 
AKROYD 

In [2]: import MySQLdb.cursors 
In [3]: import MySQLdb 
In [4]: cOnn= MySQLdb.connect(user='root',passwd='oracle',host='127.0.0.1',db='sakila',cursorclass=MySQLdb.cursors.DictCursor) 
In [5]: cur = conn.cursor() 
In [6]: v_sql = "select actor_id,last_name from actor limit 2" 
In [7]: cur.execute(v_sql) 
Out[7]: 2L 
In [8]: results = cur.fetchone() 
In [9]: print results['actor_id'] 
58 
In [10]: print results['last_name'] 
AKROYD 

[root@DataHacker Desktop]# cat sa.py 
import sqlalchemy as sa 
engine = sa.create_engine('mysql://root:oracle@127.0.0.1/testdb',pool_recycle=3600) 
metadata = sa.MetaData() 

In [3]: t = Table('t',metadata, 
   ...:        Column('id',Integer), 
   ...:        Column('name',VARCHAR(20)), 
   ...:        mysql_engine='InnoDB', 
   ...:        mysql_charset='utf8' 
   ...:       ) 
 
In [4]: t.create(bind=engine) 

有2种方式，其一： 
In [5]: t.drop(bind=engine,checkfirst=True)  
另一种是： 
In [5]: metadata.drop_all(bind=engine,checkfirst=True)，其中可以借助tables属性指定要删除的对象 

3 .1 primary key 
下面2种方式都可以，一个是列级，一个是表级 
In [7]: t_pk_col = Table('t_pk_col',metadata,Column('id',Integer,primary_key=True),Column('name',VARCHAR(20))) 
In [8]: t_pk_col.create(bind=engine) 
In [9]: t_pk_tb = Table('t_pk_01',metadata,Column('id',Integer),Column('name',VARCHAR(20)),PrimaryKeyConstraint('id','name',name='prikey')) 
In [10]: t_pk_tb.create(bind=engine) 
3.2 Foreign Key 
In [13]: t_fk = Table('t_fk',metadata,Column('id',Integer,ForeignKey('t_pk.id'))) 
In [14]: t_fk.create(bind=engine) 
In [15]: t_fk_tb = Table('t_fk_tb',metadata,Column('col1',Integer),Column('col2',VARCHAR(10)),ForeignKeyConstraint(['col1','col2'],['t_pk.id','t_pk.name'])) 
In [16]: t_fk_tb.create(bind=engine) 
3.3 unique 
In [17]: t_uni = Table('t_uni',metadata,Column('id',Integer,unique=True)) 
In [18]: t_uni.create(bind=engine) 
In [19]: t_uni_tb = Table('t_uni_tb',metadata,Column('col1',Integer),Column('col2',VARCHAR(10)),UniqueConstraint('col1','col2')) 
In [20]: t_uni_tb.create(bind=engine) 
3.4 check 
   虽然能成功，但MySQL目前尚未支持check约束。这里就不举例了。 
3.5 not null 
In [21]: t_null = Table('t_null',metadata,Column('id',Integer,nullable=False)) 
In [22]: t_null.create(bind=engine) 

4.1 例子：insert 
In [23]: t_def_inser = Table('t_def_inser',metadata,Column('id',Integer),Column('name',VARCHAR(10),server_default='cc')) 
In [24]: t_def_inser.create(bind=engine) 
3.2 例子：update 
In [25]: t_def_upda = Table('t_def_upda',metadata,Column('id',Integer),Column('name',VARCHAR(10),server_Onupdate='DataHacker')) 
In [26]: t_def_upda.create(bind=engine) 
3.3 例子：Passive  
In [27]: t_def_pass = Table('t_def_pass',metadata,Column('id',Integer),Column('name',VARCHAR(10),DefaultClause('cc'))) 
In [28]: t_def_pass.create(bind=engine) 

版本： 
[root@DataHacker ~]# ./sesc.py --version 
1.0 
查看帮助： 
[root@DataHacker ~]# ./sesc.py -h 
Usage: sesc.py [options]   [...] 
Options: 
 --version       show program's version number and exit 
 -h, --help      show this help message and exit 
 -q TERM        assign where predicate 
 -c COL, --column=COL assign query column 
 -t TABLE       assign query table 
 -f, --format     -f must match up -o 
 -o OUTFILE      assign output file 
我们要的效果： 
[root@DataHacker ~]# ./sesc.py -t actor -c last_name -q s% -f -o output.txt 
[root@DataHacker ~]# cat output.txt 
************ 1 row ******************* 
actor_id: 180 
first_name: JEFF 
last_name: SILVERSTONE 
last_update: 2006-02-15 04:34:33 
************ 2 row ******************* 
actor_id: 195 
first_name: JAYNE 
last_name: SILVERSTONE 
last_update: 2006-02-15 04:34:33 
......<此处省略大部分输出>...... 

#!/usr/bin/env python
import optparse
from dbapi import *

#构造OptionParser实例，配置期望的选项
parser = optparse.OptionParser(usage="%prog [options]   [...]",version='1.0',)
#定义命令行选项，用add_option一次增加一个
parser.add_option("-q",action="store",type="string",dest="term",help="assign where predicate")
parser.add_option("-c","--column",action="store",type="string",dest="col",help="assign query column")
parser.add_option("-t",action="store",type="string",dest="table",help="assign query table")
parser.add_option("-f","--format",action="store_true",dest="format",help="-f must match up -o")
parser.add_option("-o",action="store",type="string",dest="outfile",help="assign output file")
#解析命令行
options,args = parser.parse_args()
#把上述dest值赋给我们自定义的变量
table = options.table
column = options.col
term = options.term
format = options.format
#实现动态读查询
statement = "select * from %s where %s like '%s'"%(table,column,term)
cur = conn.cursor()
cur.execute(statement)
results = cur.fetchall()
#模拟 \G 输出形式
if format is True:
 columns_query = "describe %s"%(table)
 cur.execute(columns_query)
 heards = cur.fetchall()
 column_list = []
 for record in heards:
  column_list.append(record[0])
 output = ""
 count = 1
 for record in results:
  output = output + "************ %s row ************\n\n"%(count)
  for field_no in xrange(0, len(column_list)):
   output = output + column_list[field_no]+ ": " + str(record[field_no]) + "\n"
  output = output + "\n"
  count = count + 1
else:
 output = []
 for record in xrange(0,len(results)):
  output.append(results[record])
 output = ''.join(output)
#把输出结果定向到指定文件
if options.outfile:
 outfile = options.outfile
 with open(outfile,'w') as out:
  out.write(output)
else:
 print output
#关闭游标与连接
conn.close()
cur.close()