一、數據庫基本操作
1. 想允許在數據庫寫中文，可在創建數據庫時用下面命令
create database zcl charset utf8;
2. 查看students表結構
desc students;
3. 查看創建students表結構的語句
show create table students;
4. 刪除數據庫
drop database zcl;
5. 創建一個新的字段
alter table students add column nal char(64);
PS: 本人是很討厭上面這種“簡單解釋+代碼”的博客。其實我當時在mysql終端寫了很多的實例，不過因為當時電腦運行一個看視頻的軟件，導致我無法Ctrl+C/V。現在懶了哈哈~~
二、python連接數據庫
python3不再支持mysqldb。其替代模塊是PyMySQL。本文的例子是在python3.4環境。
1. 安裝pymysql模塊
pip3 install pymysql
2. 連接數據庫，插入數據實例
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import pymysql#生成實例，連接數據庫zclconn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')#生成游標，當前實例所處狀態cur = conn.cursor()#插入數據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() #實例提交命令 cur.close()conn.close()print(reCount) |
查看結果:
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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. 獲取數據
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import pymysqlconn = 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() #獲取一條數據res2 = cur.fetchmany(3) #獲取3條數據res3 = cur.fetchall() #獲取所有(元組格式)print(res)print(res2)print(res3)conn.commit()cur.close()conn.close() |
輸出:
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(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
事務回滾是在數據寫到數據庫前執行的，因此事務回滾conn.rollback()要在實例提交命令conn.commit()之前。只要數據未提交就可以回滾，但回滾后ID卻是自增的。請看下面的例子:
插入3條數據(注意事務回滾):
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import pymysql#連接數據庫zclconn=pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')#生成游標，當前實例所處狀態cur=conn.cursor()#插入數據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() #事務回滾conn.commit() #實例提交命令 cur.close()conn.close()print(reCount) |
未執行命令前與執行命令后(包含回滾操作)(注意ID號): 未執行上面代碼與執行上面代碼的結果是一樣的!!因為事務已經回滾，故students表不會增加數據!
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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 |
執行命令后(不包含回滾操作):只需將上面第11行代碼注釋。
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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：雖然事務回滾了，但ID還是自增了，不會因回滾而取消，但這不影響數據的一致性（底層的原理我不清楚~）
四、批量插入數據
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import pymysql#連接數據庫zclconn = pymysql.connect(host='127.0.0.1', user='root', passwd='root', db='zcl')#生成游標，當前實例所處狀態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"),]#插入數據reCount = cur.executemany('insert into students(name,sex,age,tel,nal) values(%s,%s,%s,%s,%s)', li)#conn.rollback() #事務回滾conn.commit() #實例提交命令cur.close()conn.close()print(reCount) |
pycharm下輸出: 5
mysql終端顯示:
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mysql> select* from students; #插入數據前+----+-------+--------+-----+-------------+------+| 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 setmysql> mysql> select* from students; #插入數據后+----+-------+--------+-----+-------------+------+| 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 |
以上就是本文的全部內容，希望本文的內容對大家的學習或者工作能帶來一定的幫助，同時也希望多多支持服務器之家！
原文鏈接：http://www.cnblogs.com/0zcl/p/6477042.html
