python informixDB库的使用

一、

Doingitthehardway:

cur.execute("select*fromorderswherecustomer_num=104") row=cur.fetchone()

whilerow!=None:

print"Order%swasplacedon%s."%(row[0],row[1])

row=cur.fetchone()

Usingcursorsasiteratorsismucheasier:

cur.execute("select*fromorderswherecustomer_num=104") forrowincur:

print"Order%swasplacedon%s."%(row[0],row[1])

二、

ColumnAccessAlternatives

Bydefault,rowsarereturnedastuplesaccordingtoDB-APIstandard,which

requirescolumnaccessbynumber.Dictionarycursorsreturnrowsas

dictionariesthatallowcolumnaccessbyname:

dictcur=conn.cursor(rowformat=informixdb.ROW_AS_DICT)

dictcur.execute("select*fromorderswherecustomer_num=104") forrowindictcur:

print"Order%swasplacedon%s.”,(row['order_num'],

row['order_date'])

Objectcursorsofferamoreconcisewayofaccessingcolumnsbyname:

objcur=conn.cursor(rowformat=informixdb.ROW_AS_OBJECT)

objcur.execute("select*fromorderswherecustomer_num=104") forrowinobjcur:

print"Order%swasplacedon%s."%(row.order_num,

row.order_date)

三、NamedCursor

Explicitlynamedcursorsareusefulasupdateordeletecursors:

price_increase={'SMT':4,'HSK':5,'SHM':3}

updcur=conn.cursor(name="updcur",rowformat=informixdb.ROW_AS_OBJECT)

updcur.execute("select*fromstockforupdateofunit_price")

forrowinupdcur:

increase=price_increase.get(row.manu_code,None)

ifincrease!=None:

newprice=row.unit_price*(1.0+increase/100.0)

cur.execute("updatestocksetunit_price=?wherecurrentofupdcur",

[newprice])

四、BulkExecution

names=[

(“Jonathan”,“Leffler”),

(“Darryl”,“Priest”),

(“Carsten”,“Haese”)

]

cur.executemany(“””

insertintocustomer(fname,lname)values(?,?) “””,names)

Forinsertstatements,executemanyemploysaninsertcursor“underthehood”when

possible.

五、PreparedStatements

get_manu_name=conn.cursor()

get_manu_name.prepare(“””

selectmanu_namefrommanufactwheremanu_code=? “””)

whileTrue:

manu_code=raw_input(“Enteramanufacturercode:“)

ifmanu_code==””:break

get_manu_name.execute(None,[manu_code])

manu_name=get_manu_name.fetchone()[0]

printmanu_name

六、ScrollCursor

scrollcurs=conn.cursor(scroll=True)

scrollcurs.execute(“select*fromcustomerorderbycustomer_num”) scrollcurs.scroll(10,”absolute”)

printscrollcurs.fetchone()

scrollcurs.scroll(-5,”relative”)

printscrollcurs.fetchone()

七、ErrorHandling

ydefault,errorconditionsraisePythonexceptions:

my_sqlcode=0

try:

cur.execute("sleect*fromsystables") exceptinformixdb.Error,e:

my_sqlcode=e.sqlcode

printmy_sqlcode

Anerrorhandlercallbackcanbesetuptocustomizeerrorhandling.