[DB-SIG] mysql string length?

Lukasz Szybalski szybalski at gmail.com
Tue Apr 18 17:46:45 CEST 2006


On 4/17/06, engelbert.gruber at ssg.co.at <engelbert.gruber at ssg.co.at> wrote:
> On Mon, 17 Apr 2006, Andy Todd wrote:
>
> >>>>>> stmt = "INSERT INTO table_x (body) VALUES (%s)" # [1]
> >>>>>> cursor.execute(stmt, (body,))
> >>> [1] note that there are no quote marks around the %s
> >>
> >> this works here (debian testing, python 2.3.5, 4.0.21) ::
> >>
> >> import MySQLdb
> >> """
> >> create table table_x (
> >>    id int auto_increment primary key,
> >>    body text
> >>    )
> >> """
> >> db = MySQLdb.connect(passwd="",db="test")
> >> c = db.cursor()
> >> body = "0....5...."*28
> >> sql = "INSERT INTO table_x (body) VALUES('%s')"
> >> c.execute( sql % (body))
> >> c.execute("select body from table_x")
> >> for row in c.fetchall():
> >>      print len(row[0])
> >>
> >> i wont bet on fetching 1Mb.
> >>
> >> cheers
> >
> > You've just repeated the original poster's code. As I suggested the problem
> > is that he's using string substitution when he should be using parameter
> > substitution. In these cases %s means two completely different things.
>
> yes but it works here, even with ``body = "0....5...."*280`` so i cannot
> blame it on not using 'paramstyle', or what ?
>
> > Please read the sections on 'paramstyle' and the cursor '.execute' method in
> > the DB-API 2.0 definition [1].
>
> of course you are right it is ::
>
>    c.execute("INSERT INTO table_x (body) VALUES('%s')"% (body))
>
> or paramstyle without quotes ::
>
>    c.execute(INSERT INTO table_x (body) VALUES(%s)", (body))
>
> but both work here with bodylength up to 65535 bytes not 255.
>
> sorry for dupplication, but i fail to see the point.
>
>

Ok, I'm almost there. Thank you.
So i finally realized that the length is not a problem but the actual
body. The body includes characters such as " ' ", so ( I'm, I'll, etc)
which cause it to give an error.

>>>body="helo I'm here,I'll be there"
>>> body=body *15

When i try :
c.execute("Insert into table_x(body) VALUES(%s)",(body))
This will work but how do i make :

sql="Insert into table_x(body) VALUES(%s)",(body)
c.execute(sql)  #complains that i give it a tuple, which i did when
you look at sql

One problem i see here is that it works in one way but no the other.
So how do i add id and  make it work both ways?

c.execute("Insert into  table_x(id,body) VALUES(%d,%s)",(id),(body))  
??does not work

I'm not familiar with ('pyformat'      Python extended format codes,
e.g. '...WHERE name=%(name)s' ), therefore i would prefer to use
"insert into table_x(id,body)VALUES('%d','%s')" % (id,body)

-How to account for " I'll " in a body?
-When would i HAVE to use pyformat? Can everything be done in
'format'        ANSI C printf format codes,  e.g. '...WHERE name=%s'

Thanks,
Lukasz


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