用Python开发MySQL脚本

复杂的数据库操作
下面通过一个脚本animal.py来演示如何解决复杂的数据库操作，这里给出完整的animal.py代码。
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#animal.py：创建动物表并从中检索信息
import sys
import MySQLdb
#连接到MySQL服务器
try:
conn = MySQLdb.connect (host = "localhost",
user = "testuser",
passwd = "testpass",
db = "test")
except MySQLdb.Error, e:
print "Error %d: %s" % (e.args[0], e.args[1])
sys.exit (1)
#创建动物表并填充内容
try:
cursor = conn.cursor ()
cursor.execute ("DROP TABLE IF EXISTS animal")
cursor.execute ("""
CREATE TABLE animal
(
name CHAR(40),
category CHAR(40)
)
""")
cursor.execute ("""
INSERT INTO animal (name, category)
VALUES
('snake', 'reptile'),
('frog', 'amphibian'),
('tuna', 'fish'),
('racoon', 'mammal')
""")
print "Number of rows inserted: %d" % cursor.rowcount
#使用fetchone()进行循环提取
cursor.execute ("SELECT name, category FROM animal")
while (1):
row = cursor.fetchone ()
if row == None:
break
print "%s, %s" % (row[0], row[1])
print "Number of rows returned: %d" % cursor.rowcount
#使用fetchall()进行循环提取
cursor.execute ("SELECT name, category FROM animal")
rows = cursor.fetchall ()
for row in rows:
print "%s, %s" % (row[0], row[1])
print "Number of rows returned: %d" % cursor.rowcount
#发出修改名称的语句，共两种方式，第一种是在语句字符串
#中使用数据值的字面值，第二种是使用位置标识符
cursor.execute ("""
UPDATE animal SET name = 'turtle'
WHERE name = 'snake'
""")
print "Number of rows updated: %d" % cursor.rowcount
cursor.execute ("""
UPDATE animal SET name = %s
WHERE name = %s
""", ("snake", "turtle"))
print "Number of rows updated: %d" % cursor.rowcount
#创建一个字典游标，这样就可以使用位置而非名称来访问数据列中的值了。
cursor.close ()
cursor = conn.cursor (MySQLdb.cursors.DictCursor)
cursor.execute ("SELECT name, category FROM animal")
result_set = cursor.fetchall ()
for row in result_set:
print "%s, %s" % (row["name"], row["category"])
print "Number of rows returned: %d" % cursor.rowcount
cursor.close ()
except MySQLdb.Error, e:
print "Error %d: %s" % (e.args[0], e.args[1])
sys.exit (1)
conn.commit ()
conn.close ()
该脚本使用一个表来存储动物的名称和类别：