Python操作PostgreSql数据库的方法(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

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

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!')

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')

• 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()

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()

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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