Fetching records using fetchone() and fetchmany()

阿新 • • 發佈：2018-12-29

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Up until now we have been using fetchall() method of cursor object to fetch the records. This process of accessing all records in one go is not every efficient. As a result MySQLdb has fetchone() and fetchmany() methods of cursor object to fetch records more efficiently.

Method	Description
fetchone()	This method returns one record as a tuple, If there are no more records then it returns None
fetchmany(number_of_records)	This method accepts number of records to fetch and returns tuple where each records itself is a tuple. If there are not more records then it returns an empty tuple.

Using fetchone()

from __future__ import print_function

import MySQLdb as my

try:

    db = my.connect(host="127.0.0.1",
                    user="root",
                    passwd="",
                    db="world"
                    )

    cursor = db.cursor()

    sql = "select * from city where id < 10"
    number_of_rows = cursor.execute(sql)

    print(cursor.fetchone())  # fetch the first row only

    db.close()

except my.DataError as e:
    print("DataError")
    print(e)

except my.InternalError as e:
    print("InternalError")
    print(e)

except my.IntegrityError as e:
    print("IntegrityError")
    print(e)

except my.OperationalError as e:
    print("OperationalError")
    print(e)

except my.NotSupportedError as e:
    print("NotSupportedError")
    print(e)

except my.ProgrammingError as e:
    print("ProgrammingError")
    print(e)

except :
    print("Unknown error occurred")

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from__future__importprint_functionimportMySQLdb asmytry:db=my.connect(host="127.0.0.1",user="root",passwd="",db="world")cursor=db.cursor()sql="select * from city where id < 10"number_of_rows=cursor.execute(sql)print(cursor.fetchone())# fetch the first row onlydb.close()exceptmy.DataError ase:print("DataError")print(e)exceptmy.InternalError ase:print("InternalError")print(e)exceptmy.IntegrityError ase:print("IntegrityError")print(e)exceptmy.OperationalError ase:print("OperationalError")print(e)exceptmy.NotSupportedError ase:print("NotSupportedError")print(e)exceptmy.ProgrammingError ase:print("ProgrammingError")print(e)except:print("Unknown error occurred")

Looping over the result using fetchone()

from __future__ import print_function

import MySQLdb as my

try:

    db = my.connect(host="127.0.0.1",
                    user="root",
                    passwd="",
                    db="world"
                    )

    cursor = db.cursor()

    sql = "select * from city where id < 10"
    number_of_rows = cursor.execute(sql)

    while True:
        row = cursor.fetchone()
        if row == None:
            break
        print(row)

    db.close()

except my.DataError as e:
    print("DataError")
    print(e)

except my.InternalError as e:
    print("InternalError")
    print(e)

except my.IntegrityError as e:
    print("IntegrityError")
    print(e)

except my.OperationalError as e:
    print("OperationalError")
    print(e)

except my.NotSupportedError as e:
    print("NotSupportedError")
    print(e)

except my.ProgrammingError as e:
    print("ProgrammingError")
    print(e)

except :
    print("Unknown error occurred")

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051

from__future__importprint_functionimportMySQLdb asmytry:db=my.connect(host="127.0.0.1",user="root",passwd="",db="world")cursor=db.cursor()sql="select * from city where id < 10"number_of_rows=cursor.execute(sql)whileTrue:row=cursor.fetchone()ifrow==None:breakprint(row)db.close()exceptmy.DataError ase:print("DataError")print(e)exceptmy.InternalError ase:print("InternalError")print(e)exceptmy.IntegrityError ase:print("IntegrityError")print(e)exceptmy.OperationalError ase:print("OperationalError")print(e)exceptmy.NotSupportedError ase:print("NotSupportedError")print(e)exceptmy.ProgrammingError ase:print("ProgrammingError")print(e)except:print("Unknown error occurred")

Using fetchmany()

from __future__ import print_function

import MySQLdb as my

try:

    db = my.connect(host="127.0.0.1",
                    user="root",
                    passwd="",
                    db="world"
                   )

    cursor = db.cursor()

    sql = "select * from city where id < 10"
    number_of_rows = cursor.execute(sql)

    print(cursor.fetchmany(2))  # fetch first 2 rows only

    db.close()

except my.DataError as e:
    print("DataError")
    print(e)

except my.InternalError as e:
    print("InternalError")
    print(e)

except my.IntegrityError as e:
    print("IntegrityError")
    print(e)

except my.OperationalError as e:
    print("OperationalError")
    print(e)

except my.NotSupportedError as e:
    print("NotSupportedError")
    print(e)

except my.ProgrammingError as e:
    print("ProgrammingError")
    print(e)

except :
    print("Unknown error occurred")

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647

from__future__importprint_functionimportMySQLdb asmytry:db=my.connect(host="127.0.0.1",user="root",passwd="",db="world")cursor=db.cursor()sql="select * from city where id < 10"number_of_rows=cursor.execute(sql)print(cursor.fetchmany(2))# fetch first 2 rows onlydb.close()exceptmy.DataError ase:print("DataError")print(e)exceptmy.InternalError ase:print("InternalError")print(e)exceptmy.IntegrityError ase:print("IntegrityError")print(e)exceptmy.OperationalError ase:print("OperationalError")print(e)exceptmy.NotSupportedError ase:print("NotSupportedError")print(e)exceptmy.ProgrammingError ase:print("ProgrammingError")print(e)except:print("Unknown error occurred")

Looping over the result using fetchmany()

from __future__ import print_function

import MySQLdb as my

try:

    db = my.connect(host="127.0.0.1",
                    user="root",
                    passwd="",
                    db="world"
                   )

    cursor = db.cursor()

    sql = "select * from city where id < 10"
    number_of_rows = cursor.execute(sql)

    while True:
        two_rows = cursor.fetchmany(2)
        if two_rows == ():
            break
        print(two_rows)

    db.close()

except my.DataError as e:
    print("DataError")
    print(e)

except my.InternalError as e:
    print("InternalError")
    print(e)

except my.IntegrityError as e:
    print("IntegrityError")
    print(e)

except my.OperationalError as e:
    print("OperationalError")
    print(e)

except my.NotSupportedError as e:
    print("NotSupportedError")
    print(e)

except my.ProgrammingError as e:
    print("ProgrammingError")
    print(e)

except :
    print("Unknown error occurred")

123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051

from__future__importprint_functionimportMySQLdb asmytry:db=my.connect(host="127.0.0.1",user="root",passwd="",db="world")cursor=db.cursor()sql="select * from city where id < 10"number_of_rows=cursor.execute(sql)whileTrue:two_rows=cursor.fetchmany(2)iftwo_rows==():breakprint(two_rows)db.close()exceptmy.DataError ase:print("DataError")print(e)exceptmy.InternalError ase:print("InternalError")print(e)exceptmy.IntegrityError ase:print("IntegrityError")print(e)exceptmy.OperationalError ase:print("OperationalError")print(e)exceptmy.NotSupportedError ase:print("NotSupportedError")print(e)exceptmy.ProgrammingError ase:print("ProgrammingError")print(e)except:print("Unknown error occurred")

Fetching records using fetchone() and fetchmany()

Using fetchone()

Looping over the result using fetchone()

Using fetchmany()

Looping over the result using fetchmany()

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Fetching records using fetchone() and fetchmany()

Using fetchone()

Looping over the result using fetchone()

Using fetchmany()

Looping over the result using fetchmany()

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