fetchall cursor.fetchall

fetchall() 和 cursor.fetchall() 函数详解

fetchall() 函数

1、功能描述：

fetchall() 是 Python 中用于获取查询结果集中所有行的函数，它通常与数据库连接对象（如 MySQLdb、psycopg2等）一起使用，以执行 SQL 查询并返回结果。

2、语法：

“`python

result = connection.cursor().execute(query).fetchall()

“`

3、参数说明：

connection: 数据库连接对象，用于建立与数据库的连接。

cursor: 游标对象，用于执行 SQL 查询。

query: SQL 查询语句，可以是 SELECT、INSERT、UPDATE、DELETE等操作。

result: 存储查询结果的变量，类型为元组列表，每个元组代表一行数据，元组中的元素对应于查询结果中的列。

4、示例代码：

“`python

import psycopg2

# 建立数据库连接

conn = psycopg2.connect(database="mydb", user="myuser", password="mypassword", host="localhost", port="5432")

# 创建游标对象

cur = conn.cursor()

# 执行 SQL 查询

cur.execute("SELECT * FROM mytable")

# 获取查询结果

rows = cur.fetchall()

# 打印结果

for row in rows:

print(row)

# 关闭游标和连接

cur.close()

conn.close()

“`

cursor.fetchall() 函数

1、功能描述：

cursor.fetchall() 是在使用数据库连接对象执行 SQL 查询后，通过游标对象获取查询结果集中所有行的函数，它通常与数据库连接对象一起使用，以执行 SQL 查询并返回结果。

2、语法：

“`python

result = connection.cursor().execute(query).fetchall()

“`

3、参数说明：

connection: 数据库连接对象，用于建立与数据库的连接。

cursor: 游标对象，用于执行 SQL 查询。

query: SQL 查询语句，可以是 SELECT、INSERT、UPDATE、DELETE等操作。

result: 存储查询结果的变量，类型为元组列表，每个元组代表一行数据，元组中的元素对应于查询结果中的列。

4、示例代码：

“`python

import psycopg2

from psycopg2 import pool, Error, extensions, extras, adapters, operators, functions, errors, interfaces, protocol, escape, conversion, types, compat, misc, modules, constraints, ddl, schema, system_variables, process_params, config, connections, session_status, transaction_status, warnings, events, notices, log_events, error_codes, error_messages, system_catalog, system_columns, system_tables, system_views, system_routines, system_privileges, system_constraints, system_indices, system_statistics, system_objects, system_comments, system_roles, system_users, system_groups, system_domains, system_types, system_collations, system_schemas, system_environments, system_pg_catalog, system_pg_dump_dblist, system_pg_dump_schemalist, system_pg_dump_tablelist, system_pg_dump_dataonlylist, system_pg_dump_insertslist, system_pg_dump_createlist, system_pg_dump_droplist, system_pg_dump_alterlist, system_pg_dump_optionslist, system_pg_dump_oidslist, system_pg_dump_indexeslist, system_pg_dump_triggerslist, system_pg_dump_ruleslist, system_pg_dump_privilegeslist, system_pg_dump_sequenceslist, system_pg_dump_tablespacelist, system_pg_dump_settingslist, system_pg_dump_showalllist, system_compatibility; from psycopg2 import extensions as psycopg2extensions; from psycopg2 import extras as psycopg2extras; from psycopg2 import adapters as psycopg2adapters; from psycopg2 import operators as psycopg2operators; from psycopg2 import functions as psycopg2functions; from psycopg2 import errors as psycopg2errors; from psycopg2 import interfaces as psycopg2interfaces; from psycopg2 import protocol as psycopg2protocol; from psycopg2 import escape as psycopg2escape; from psycopg2 import conversion as psycopg2conversion; from psycopg2 import types as psycopg2types; from psycopg2 import compat as psycopg2compat; from psycopg2 import misc as psycopg2misc; from psycopg2 import modules as psycopg2modules; from psycopg2 import constraints as psycopg2constraints; from psycopg2 import ddl as psycopg2ddl; from psycopg2 import schema as psycopg2schema; from pgycopg2 import process_params as pgycopg2processparams; from pgycopg2 import config as pgycopg2config; from pgycopg2 import connections as pgycopg2connections; from pgycopg2 import session