mysql pymysql ,分頁

pymysql 

# 1.先安裝pymysql 模塊 pip3 install pymysql
import pymysql
# 至關於mysql的客戶端程序
# 前端中獲取的用戶名和密碼
username = input('請輸入用戶名:')
pwd = input('請輸入密碼:')



# 創建鏈接
conn = pymysql.connect(
    host = '127.0.0.1',
    port = 3306,
    db = 'db20',
    user = 'root',
    password='',
    charset ='utf8'
)

# 建立遊標
cur = conn.cursor()

# select * from userinfo where name = 'alex' and password = '123';
sql  = "select * from userinfo where name = '%s' and password = '%s'" %(username,pwd)
print(sql)

# 執行sql  返回是查詢的成功的記錄
result = cur.execute(sql) 使用這個能夠防止sql注入

print(result)

# 遊標關閉  鏈接關閉
cur.close()
conn.close()

if result:

    # 響應 數據 到前端
    print('登陸成功')

else:
    print('登陸失敗')

　　

sql  = "select * from userinfo where name = %(name)s and password = %(password)s"
print(sql)

# sql  --

# 執行sql  返回是查詢的成功的記錄
result = cur.execute(sql,{"name":username,"password":pwd})

print(result)# 字典

 

# 1.先安裝pymysql 模塊 pip3 install pymysql
import pymysql
# 至關於mysql的客戶端程序


# 創建鏈接
conn = pymysql.connect(
    host = '127.0.0.1',
    port = 3306,
    db = 'db20',
    user = 'root',
    password='',
    charset ='utf8'
)

# 建立遊標
cur = conn.cursor()

# 插入
# select * from userinfo where name = 'alex' and password = '123';
sql = "insert into userinfo(name,password) values (%s,%s)"


# 更改
# sql = "update userinfo set name = %s where id = 3"
# 更改
# sql = "delete from userinfo  where id = 3"

# print(sql)

# sql  --

# 執行sql 插入數據 刪除數據 更改數據 必定記得commit()
# 插入一條數據
# result = cur.execute(sql)

# 插入多條數據
result = cur.executemany(sql,[('alex2','321'),('alex3','678')])



print(result)

# 必定要提交
conn.commit()
# 遊標關閉  鏈接關閉
cur.close()
conn.close()

　　查詢

:

 建立遊標 查詢出來的記錄 是字典的形式
cur = conn.cursor(cursor=pymysql.cursors.DictCursor)

# select * from userinfo where name = 'alex' and password = '123';
sql  = "select * from userinfo"
print(sql)

# sql  --

# 執行sql  返回是查詢的成功的記錄
result = cur.execute(sql)
print(result)



# rows = cur.fetchone()
# print(rows)
# rows = cur.fetchone()
# print(rows)
# rows = cur.fetchone()
# print(rows)
# rows = cur.fetchone()
# print(rows)

# 查詢多條數據
# rows = cur.fetchmany(2)

# 查詢全部的數據
rows = cur.fetchall()
print(rows)

elect * from userinfo where name = 'alex' and password = '123';
sql  = "select * from userinfo"
print(sql)

# sql  --

# 執行sql  返回是查詢的成功的記錄
result = cur.execute(sql)
print(result)

rows = cur.fetchone()
print(rows)
rows = cur.fetchone()
print(rows)

cur.scroll(1,mode='absolute')
rows = cur.fetchone()
print(rows)

# rows = cur.fetchone()
# print(rows)
# rows = cur.fetchone()
# print(rows)
# rows = cur.fetchone()
# print(rows)

只有一頁 和下一頁

1,記錄當前頁的最大id或者最小的id

下一頁:

select * from user where id > max_id limit 10,

select 8 from user where id< min order by id desc limit 10;

2,頁面有頁碼的狀況

select * from user where id in (

　　select id from (select *from user where id > pre_max_id limit (cu)max_id-pre_max_id)*10 ) as A order by A.id desc limit 10);

 

　　select * from (select * from user where id > 1500011 limit 30) as  A order by id order by desc;