Python操作PostgreSql数据库（基本的增删改查）

操作数据库最快的方式当然是直接用使用SQL语言直接对数据库进行操作，但是偶尔我们也会碰到在代码中操作数据库的情况，我们可能用ORM类的库对数控库进行操作，但是当需要操作大量的数据时，ORM的数据显的太慢了。在python中，遇到这样的情况，我推荐使用psycopg2操作postgresql数据库

psycopg2

官方文档传送门： http://initd.org/psycopg/docs/index.html

简单的增删改查

连接

连接pg并创建表

PG_SQL_LOCAL = { 'database': 'postgres', 'user': 'postgres', 'password': "8dsa581", # 'host':'10.27.78.1', 'host': 'localhost'}def connectPostgreSQL(): conn = psycopg2.connect(**PG_SQL_LOCAL) print('connect successful!') cursor = conn.cursor() cursor.execute(''' create table public.members( id integer not null primary key, name varchar(32) not null, password varchar(32) not null, singal varchar(128) )''') conn.commit() conn.close() print('table public.member is created!')

增

一条一条的增加数据

def insertOperate(): conn = psycopg2.connect(**PG_SQL_LOCAL) cursor = conn.cursor() cursor.execute("insert into public.member(id,name,password,singal)\values(1,'member0','password0','signal0')") cursor.execute("insert into public.member(id,name,password,singal)\values(2,'member1','password1','signal1')") cursor.execute("insert into public.member(id,name,password,singal)\values(3,'member2','password2','signal2')") cursor.execute("insert into public.member(id,name,password,singal)\values(4,'member3','password3','signal3')") row = conn.fetchone() print(row) conn.commit() conn.close() print('insert records into public.memmber successfully')

查

• fetchall() 一次性获取所有数据
• fetchmany() 一次值提取2000条数据（使用服务端的游标）

def selectOperate(): conn = psycopg2.connect(**PG_SQL_LOCAL) cursor = conn.cursor() cursor.execute("select id,name,password,singal from public.member where id>2") # rows = cursor.fetchall() # for row in rows: # print('id=', row[0], ',name=', row[1], ',pwd=', row[2], ',singal=', row[3],) while True: rows = cursor.fetchmany(2000) if not rows: break for row in rows: # print('id=', row['id'], ',name=', row['name'], ',pwd=', row['pwd'], ',singal=', row['singal'],) rid,name,pwd,singal = row print(rid,name,pwd,singal) # print('id=', row[0], ',name=', row[1], ',pwd=', row[2], ',singal=', row[3], ) conn.close()

改

更新数据

def updateOperate(): conn = psycopg2.connect(**PG_SQL_LOCAL) cursor=conn.cursor() result = cursor.execute("update public.member set name='member X' where id=3") print(result) conn.commit() print("Total number of rows updated :", cursor.rowcount) cursor.execute("select id,name,password,singal from public.member") rows=cursor.fetchall() for row in rows: print('id=',row[0], ',name=',row[1],',pwd=',row[2],',singal=',row[3],'\n') conn.close()

删

删除数据

def deleteOperate(): conn = psycopg2.connect(**PG_SQL_LOCAL) cursor = conn.cursor() cursor.execute("select id,name,password,singal from public.member") rows = cursor.fetchall() for row in rows: print('id=', row[0], ',name=', row[1], ',pwd=', row[2], ',singal=', row[3], '\n') print('begin delete') cursor.execute("delete from public.member where id=2") conn.commit() print('end delete') print("Total number of rows deleted :", cursor.rowcount) cursor.execute("select id,name,password,singal from public.member") rows = cursor.fetchall() for row in rows: print('id=', row[0], ',name=', row[1], ',pwd=', row[2], ',singal=', row[3], '\n') conn.close()

补充，增加的字段带有时间格式

带有时间格式是，只需要传入时间格式的字符串（‘2017-05-27'）即可，PG会自动识别

cur.execute("INSERT INTO Employee " "VALUES('Gopher', 'China Beijing', 100, '2017-05-27')")# 查询数据cur.execute("SELECT * FROM Employee")rows = cur.fetchall()for row in rows: print('name=' + str(row[0]) + ' address=' + str(row[1]) + ' age=' + str(row[2]) + ' date=' + str(row[3]), type(row[3])) # 插入数据 sql = """INSERT INTO Employees VALUES(%s, %s, %s,%s) """ var = [] var.append([row[0], row[1], row[2], row[3]]) cur.executemany(sql, var)# 提交事务conn.commit()# 关闭连接conn.close()

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