透過python操作mysql資料庫

一、資料庫基本操作

1. 想允許在資料庫寫中文，可在建立資料庫時用下面指令

CREATE database zcl charset utf8;

2. 檢視students表格結構

desc students;

3. 檢視建立students表格結構的語句

show create table students;

4. 刪除資料庫

drop database zcl;

#5 . 創建一個新的字段

alter table students add column nal char(64);　

PS: 本人很討厭上面這種“簡單解釋+代碼”的部落格。其實我當時在mysql終端機寫了很多的實例，不過因為當時電腦運行一個看影片的軟體，導致我無法Ctrl+C/V。現在懶了哈哈~~

二、python連線資料庫

python3不再支援mysqldb。其替代模組是PyMySQL。本文的例子是在python3.4環境。

1. 安裝pymysql模組

#pip3 install pymysql

# 2. 連線資料庫，插入資料實例

import pymysql
#生成实例，连接数据库zcl
conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')
#生成游标，当前实例所处状态
cur = conn.cursor()
#插入数据
reCount = cur.execute('insert into students(name, sex, age, tel, nal) values(%s, %s, %s, %s, %s)',('Jack','man',25,1351234,"CN"))
reCount = cur.execute('insert into students(name, sex, age, tel, nal) values(%s, %s, %s, %s, %s)',('Mary','female',18,1341234,"USA"))
conn.commit() #实例提交命令 
cur.close()
conn.close()
print(reCount)

#檢視結果:

##

mysql> select* from students;
+----+------+-----+-----+-------------+------+
| id | name | sex | age | tel | nal |
+----+------+-----+-----+-------------+------+
| 1 | zcl | man | 22 | 15622341234 | NULL |
| 2 | alex | man | 30 | 15622341235 | NULL |
+----+------+-----+-----+-------------+------+
rows in set

3. 取得資料

#

import pymysql
conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')
cur = conn.cursor()
reCount = cur.execute('select* from students')
res = cur.fetchone() #获取一条数据
res2 = cur.fetchmany(3) #获取3条数据
res3 = cur.fetchall() #获取所有(元组格式)
print(res)
print(res2)
print(res3)
conn.commit()
cur.close()
conn.close()

輸出:

# #

(1, 'zcl', 'man', 22, '15622341234', None)
((2, 'alex', 'man', 30, '15622341235', None), (5, 'Jack', 'man', 25, '1351234', 'CN'), (6, 'Mary', 'female', 18, '1341234', 'USA'))
()

三、事務回滾

#交易回滾是在資料寫到資料庫前執行的

，因此交易回滾conn.rollback()要在實例提交命令conn.commit()之前。

只要資料未提交就可以回滾，但回滾後ID卻是自增的。

請看下面的範例:

插入3條資料(注意交易回溯):

import pymysql
#连接数据库zcl
conn=pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')
#生成游标，当前实例所处状态
cur=conn.cursor()
#插入数据
reCount=cur.execute('insert into students(name, sex, age, tel, nal) values(%s, %s, %s, %s, %s)', ('Jack', 'man', 25, 1351234, "CN"))
reCount=cur.execute('insert into students(name, sex, age, tel, nal) values(%s,%s,%s,%s,%s)', ('Jack2', 'man', 25, 1351234, "CN"))
reCount=cur.execute('insert into students(name, sex, age, tel, nal) values(%s, %s, %s, %s, %s)', ('Mary', 'female', 18, 1341234, "USA"))
conn.rollback() #事务回滚
conn.commit() #实例提交命令 
cur.close()
conn.close()
print(reCount)

#未執行指令前與執行指令後(包含回滾操作)(注意ID號): 未執行上面程式碼與執行上面程式碼的結果是一樣的!!因為交易已經回滾，故students表不會增加資料!

mysql> select* from students;
+----+------+--------+-----+-------------+------+
| id | name | sex | age | tel | nal |
+----+------+--------+-----+-------------+------+
| 1 | zcl | man | 22 | 15622341234 | NULL |
| 2 | alex | man | 30 | 15622341235 | NULL |
| 5 | Jack | man | 25 | 1351234 | CN |
| 6 | Mary | female | 18 | 1341234 | USA |
+----+------+--------+-----+-------------+------+
rows in set

執行指令後(不包含回滾操作):只需將上面第11行程式碼註解。

mysql> select* from students;
+----+-------+--------+-----+-------------+------+
| id | name | sex | age | tel | nal |
+----+-------+--------+-----+-------------+------+
| 1 | zcl | man | 22 | 15622341234 | NULL |
| 2 | alex | man | 30 | 15622341235 | NULL |
| 5 | Jack | man | 25 | 1351234 | CN |
| 6 | Mary | female | 18 | 1341234 | USA |
| 10 | Jack | man | 25 | 1351234 | CN |
| 11 | Jack2 | man | 25 | 1351234 | CN |
| 12 | Mary | female | 18 | 1341234 | USA |
+----+-------+--------+-----+-------------+------+
rows in set

總結：雖然交易回滾了，但ID還是自增了，不會因為回滾而取消，但這不影響資料的一致性（底層的原理我不清楚~）

四、批次插入資料

#########

import pymysql
#连接数据库zcl
conn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')
#生成游标，当前实例所处状态
cur = conn.cursor()
li = [
 ("cjy","man",18,1562234,"USA"),
 ("cjy2","man",18,1562235,"USA"),
 ("cjy3","man",18,1562235,"USA"),
 ("cjy4","man",18,1562235,"USA"),
 ("cjy5","man",18,1562235,"USA"),
]
#插入数据
reCount = cur.executemany('insert into students(name,sex,age,tel,nal) values(%s,%s,%s,%s,%s)', li)
#conn.rollback() #事务回滚
conn.commit() #实例提交命令
cur.close()
conn.close()
print(reCount)

## #######pycharm下輸出: 5######mysql終端顯示:##########

mysql> select* from students; 　 #插入数据前
+----+-------+--------+-----+-------------+------+
| id | name | sex | age | tel | nal |
+----+-------+--------+-----+-------------+------+
| 1 | zcl | man | 22 | 15622341234 | NULL |
| 2 | alex | man | 30 | 15622341235 | NULL |
| 5 | Jack | man | 25 | 1351234 | CN |
| 6 | Mary | female | 18 | 1341234 | USA |
| 10 | Jack | man | 25 | 1351234 | CN |
| 11 | Jack2 | man | 25 | 1351234 | CN |
| 12 | Mary | female | 18 | 1341234 | USA |
+----+-------+--------+-----+-------------+------+
rows in set


mysql> 
mysql> select* from students;　　　#插入数据后
+----+-------+--------+-----+-------------+------+
| id | name | sex | age | tel | nal |
+----+-------+--------+-----+-------------+------+
| 1 | zcl | man | 22 | 15622341234 | NULL |
| 2 | alex | man | 30 | 15622341235 | NULL |
| 5 | Jack | man | 25 | 1351234 | CN |
| 6 | Mary | female | 18 | 1341234 | USA |
| 10 | Jack | man | 25 | 1351234 | CN |
| 11 | Jack2 | man | 25 | 1351234 | CN |
| 12 | Mary | female | 18 | 1341234 | USA |
| 13 | cjy | man | 18 | 1562234 | USA |
| 14 | cjy2 | man | 18 | 1562235 | USA |
| 15 | cjy3 | man | 18 | 1562235 | USA |
| 16 | cjy4 | man | 18 | 1562235 | USA |
| 17 | cjy5 | man | 18 | 1562235 | USA |
+----+-------+--------+-----+-------------+------+
rows in set

###更多透過python操作mysql資料庫相關文章請關注PHP中文網！ ##########