1. Introduction:
MySQL is a relational database. Other relational databases include Oracle, DB2, Sql Server, etc. Python operation of MySQL requires the use of pymsyql module, pip can be installed.
Second, the operation of MySQL steps
1. Connect to the database (IP, port number, user name, password, database name)
2. Create a cursor
3. Execute SQL
4. Get results
5. Close the cursor
6. Close the connection
1 import pymysql 2 conn = pymysql.connect ( 3 host = '192.168.1.112', 4 user = 'test', 5 passwd = '111111', 6 port = 3306, # port must be int type 7 db = 'test' , 8 charset = 'utf8' # charset must write utf8, not utf-8 9) 10 sqla = 'select * from stu limit 10;' 11 sqlb = 'insert into stu (id, name, sex) VALUE (10000, "张 流", "女"); '12 cur = conn.cursor () # Create a cursor without specifying the cursor type and return a two-dimensional tuple 13 cur = conn.cursor (cursor = pymysql.cursors.DictCursor) # Create a cursor and specify the cursor type to return a dictionary 14 cur.execute (sqla) # execute sqla 15 cur.execute (sqlb) # execute sqlb 16 conn.commit () # execute insert, delete, update statements must commit 17 res = cur.fetchall () # execute all the returned results, fetchall returns a two-dimensional array 18 res = cur.fetchone () # execute all returned results, fetchone returns the first line 19 res = cur.fetchmany (2) # execute all returned results, fetchmany passes in a number and returns how many data 20 res = cur.description # returns the information of each field in the table, description returns a two-dimensional array 21 print (res) 22 cur.close () # close the cursor 23 conn.close () # close the connection
Cursor type:
Without specifying the cursor type, ie: cur = conn.cursor (), the returned result is: ((5, 'Ben', male '), (6,' Lily ', female')), which is a two-dimensional Tuple
Specify the curson type, that is: cur = conn.cursor (cursor = pymysql.cursors.DictCursor), the returned result is:
[{'id': 5, 'name': 'Ben', 'sex': '男'}, {'id': 6, 'name': 'Lily', 'sex': '女'}]
The difference between fetchall () and fetchone ():
fetchall (): Get all the results of this SQL execution, it puts each row of data in the database table into a tuple or dictionary
fetchone (): Get a result of this SQL execution, it returns only a piece of data
If the result of the SQL statement execution is multiple data, then use fetchall (), if you can be sure that there is only one result of the SQL execution, then use fetchone ()
Third, encapsulate the function of operating the MySQL database
1 def my_db (sql, port = 3306, charset = 'utf8'): 2 import pymysql 3 host, user, passwd, db = '192.168.1.112', 'test', '111111', 'test' # define variable 4 conn = pymysql.connect (host = host, 5 user = user, 6 passwd = passwd, 7 port = port, 8 db = db, 9 charset = charset) 10 cur = conn.cursor (cursor = pymysql.cursors.DictCursor) # Create a cursor and specify the cursor type to return a dictionary 11 cur.execute (sql) # Execute statement 12 if sql.strip (). Split () [0] .upper () == 'SELECT': # Determine whether the SQL statement Start with select 13 res = cur.fetchall () 14 else: 15 conn.commit() 16 res = 'OK' 17 cur.close () # close the cursor 18 conn.close () # close the connection 19 return res
Fourth, practice
Pass in a table name, export all data and write to excel file
1 def export_excel (table_name):
2 import pymysql, xlwt
3 conn = pymysql.connect (
4 host = '118.24.3.40',
5 user = 'jxz',
6 passwd = '123456',
7 port = 3306,
8 db = 'jxz',
9 charset = 'utf8')
10 sql = 'select * from% s;'% table_name
11 cur = conn.cursor () # Create a cursor without specifying the cursor type and return a two-dimensional tuple
12 cur. execute (sql) # execute sql
13 all_data = cur.fetchall () # get all the data in the table
14 fileds = [filed [0] for filed in cur.description] # get all the fields of the table into a list
15 book = xlwt.Workbook () # Create a new excel
16 sheet = book.add_sheet ('sheet1') # Add sheet page
17 for col, filed in enumerate (fileds):
18 sheet.write (0, col, filed) # Write the table header to the first row in the excel file
19 row = 1 # Define the number of rows
20 for data in all_data: # Control line
21 for col, filed in enumerate (data): # Control column
22 sheet.write (row, col, filed)
23 row = row + 1 # Each time a row is written, add 1
24 book.save ('% s.xls'% table_name)