Python操作PostgreSql資料庫（基本的增刪改查）

操作資料庫最快的方式當然是直接用使用SQL語言直接對資料庫進行操作，但是偶爾我們也會碰到在程式碼中操作資料庫的情況，我們可能用ORM類的庫對數控庫進行操作，但是當需要操作大量的資料時，ORM的資料顯的太慢了。在python中，遇到這樣的情況，我推薦使用psycopg2操作postgresql資料庫

psycopg2

官方文件傳送門： http://initd.org/psycopg/docs/index.html

簡單的增刪改查

連線

連線pg並建立表

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

一條一條的增加資料

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,singal)\
values(2,'member1','password1','signal1')")
 cursor.execute("insert into public.member(id,singal)\
values(3,'member2','password2','signal2')")
 cursor.execute("insert into public.member(id,singal)\
values(4,'member3','password3','signal3')")
 row = conn.fetchone()
 print(row)
 conn.commit()
 conn.close()

 print('insert records into public.memmber successfully')

查

• fetchall() 一次性獲取所有資料
• fetchmany() 一次值提取2000條資料（使用服務端的遊標）

def selectOperate():
 conn = psycopg2.connect(**PG_SQL_LOCAL)
 cursor = conn.cursor()
 cursor.execute("select id,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'],row['name'],row['pwd'],row['singal'],)
  rid,pwd,singal = row
  print(rid,singal)
  # print('id=',)
 conn.close()

改

更新資料

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,singal from public.member")
 rows=cursor.fetchall()
 for row in rows:
 print('id=','\n')
 conn.close()

刪

刪除資料

def deleteOperate():
 conn = psycopg2.connect(**PG_SQL_LOCAL)
 cursor = conn.cursor()

 cursor.execute("select id,singal from public.member")
 rows = cursor.fetchall()
 for row in rows:
 print('id=','\n')

 print('begin delete')
 cursor.execute("delete from public.member where id=2")
 conn.commit()
 print('end delete')
 print("Total number of rows deleted :",'\n')
 conn.close()

補充，增加的欄位帶有時間格式

帶有時間格式是，只需要傳入時間格式的字串（‘2017-05-27'）即可，PG會自動識別

cur.execute("INSERT INTO Employee "
  "VALUES('Gopher','China Beijing',100,'2017-05-27')")
# 查詢資料
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]))

 # 插入資料
 sql = """INSERT INTO Employees VALUES(%s,%s,%s) """
 var = []
 var.append([row[0],row[3]])
 cur.executemany(sql,var)

# 提交事務
conn.commit()

# 關閉連線
conn.close()

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