I'm trying to produce the following SQL using CDBI:
select * from mytable
where ref = "foo"
and to_date(received_date, 'DD-MM-YYYY') < to_date('01-04-2011', 'DD-MM-YYYY')
The closest syntax I can think of is:
mycdbi->search_where({
ref => 'foo',
received_date => { '<' => ["to_date(?, 'DD-MM-YYYY')", '01-04-2011'] }
});
However that's not converting the column mytable.received_date using Oracle function to_date.
So what's the correct way to do it?
Ps: please don't say use DBIC as the code needs to stay in CDBI.
thanks!
Might be easiest to just use retrieve_from_sql and do it by hand:
my #things = mycdbi->retrieve_from_sql(qq{
ref = 'foo'
AND to_date(received_date, 'DD-MM-YYYY') < to_date('01-04-2011', 'DD-MM-YYYY')
});
I usually end up pushing the ORMs out of the way for any instantiation more complicated than my $thing = Thing->retrieve(x), I already know SQL so I don't need to learn yet another API that tries to implement SQL and usually does so rather poorly.
Related
I have the following select statement in ABAP:
SELECT munic~mandt VREFER BIS AB ZZELECDATE ZZCERTDATE CONSYEAR ZDIMO ZZONE_M ZZONE_T USAGE_M USAGE_T M2MC M2MT M2RET EXEMPTMCMT EXEMPRET CHARGEMCMT
INTO corresponding fields of table GT_INSTMUNIC_F
FROM ZCI00_INSTMUNIC AS MUNIC
INNER JOIN EVER AS EV on
MUNIC~POD = EV~VREFER(9).
"where EV~BSTATUS = '14' or EV~BSTATUS = '32'.
My problem with the above statement is that does not recognize the substring/offset operation on the 'ON' clause. If i remove the '(9) then
it recognizes the field, otherwise it gives error:
Field ev~refer is unknown. It is neither in one of the specified tables
nor defined by a "DATA" statement. I have also tried doing something similar in the 'Where' clause, receiving a similar error:
LOOP AT gt_instmunic.
clear wa_gt_instmunic_f.
wa_gt_instmunic_f-mandt = gt_instmunic-mandt.
wa_gt_instmunic_f-bis = gt_instmunic-bis.
wa_gt_instmunic_f-ab = gt_instmunic-ab.
wa_gt_instmunic_f-zzelecdate = gt_instmunic-zzelecdate.
wa_gt_instmunic_f-ZZCERTDATE = gt_instmunic-ZZCERTDATE.
wa_gt_instmunic_f-CONSYEAR = gt_instmunic-CONSYEAR.
wa_gt_instmunic_f-ZDIMO = gt_instmunic-ZDIMO.
wa_gt_instmunic_f-ZZONE_M = gt_instmunic-ZZONE_M.
wa_gt_instmunic_f-ZZONE_T = gt_instmunic-ZZONE_T.
wa_gt_instmunic_f-USAGE_M = gt_instmunic-USAGE_M.
wa_gt_instmunic_f-USAGE_T = gt_instmunic-USAGE_T.
temp_pod = gt_instmunic-pod.
SELECT vrefer
FROM ever
INTO wa_gt_instmunic_f-vrefer
WHERE ( vrefer(9) LIKE temp_pod ). " PROBLEM WITH SUBSTRING
"AND ( BSTATUS = '14' OR BSTATUS = '32' ).
ENDSELECT.
WRITE: / sy-dbcnt.
WRITE: / 'wa is: ', wa_gt_instmunic_f.
WRITE: / 'wa-ever is: ', wa_gt_instmunic_f-vrefer.
APPEND wa_gt_instmunic_f TO gt_instmunic_f.
WRITE: / wa_gt_instmunic_f-vrefer.
ENDLOOP.
itab_size = lines( gt_instmunic_f ).
WRITE: / 'Internal table populated with', itab_size, ' lines'.
The basic task i want to implement is to modify a specific field on one table,
pulling values from another. They have a common field ( pod = vrefer(9) ). Thanks in advance for your time.
If you are on a late enough NetWeaver version, it works on 7.51, you can use the OpenSQL function LEFT or SUBSTRING. Your query would look something like:
SELECT munic~mandt VREFER BIS AB ZZELECDATE ZZCERTDATE CONSYEAR ZDIMO ZZONE_M ZZONE_T USAGE_M USAGE_T M2MC M2MT M2RET EXEMPTMCMT EXEMPRET CHARGEMCMT
FROM ZCI00_INSTMUNIC AS MUNIC
INNER JOIN ever AS ev
ON MUNIC~POD EQ LEFT( EV~VREFER, 9 )
INTO corresponding fields of table GT_INSTMUNIC_F.
Note that the INTO clause needs to move to the end of the command as well.
field(9) is a subset operation that is processed by the ABAP environment and can not be translated into a database-level SQL statement (at least not at the moment, but I'd be surprised if it ever will be). Your best bet is either to select the datasets separately and merge them manually (if both are approximately equally large) or pre-select one and use a FAE/IN clause.
They have a common field ( pod = vrefer(9) )
This is a wrong assumption, because they both are not fields, but a field an other thing.
If you really need to do that task through SQL, I'll suggest you to check native SQL sentences like SUBSTRING and check if you can manage to use them within an EXEC_SQL or (better) the CL_SQL* classes.
I have written below SQL in an RPGLE program. Intent is to update the header file (TC400F) if no corresponding records exist in detail file (TC401F). Are there better ways of doing this? By better, I mean that would make the query run faster or would make it look more cleaner.
Exec SQL UPDATE TC400F
SET T40STS = '05',
T40OFL = '1'
WHERE T40SID = :K#T41SID AND
T40PID = :K#T41PID AND
NOT EXISTS (SELECT * FROM TC401F WHERE
T41SID = :K#T41SID AND
T41PID = :K#T41PID );
try this :
Exec SQL UPDATE TC400F f1
SET (f1.T40STS, f1.T40OFL) = ('05', '1')
WHERE f1.T40SID = :K#T41SID AND
f1.T40PID = :K#T41PID AND
NOT EXISTS
(
SELECT * FROM TC401F f2
WHERE (f1.T41SID, f1.T41PID) = (f2.T41SID, f2.T41PID)
);
You have not done anything here that explicitly restricts performance. The optimizer is pretty smart these days. Most of the things that affect SQL performance are external to the statement. Best to write the statement to be semantically correct (as you have above), and let the optimizer do it's thing. Then if you see performance issues, then investigate them with then Explain tools in Run SQL Scripts. Most likely your performance issues will derive from incorrect indexes.
Exec SQL UPDATE TC400F
SET T40STS = '05',
T40OFL = '1'
WHERE (t40sts <> '05' or t40ofl <> '1')
and T40SID = :K#T41SID
AND T40PID = :K#T41PID
and
NOT EXISTS (SELECT onefieldhere FROM TC401F WHERE
T41SID = :K#T41SID AND
T41PID = :K#T41PID );
Add a little optimistic code don't update what is already set.
Please don't make the as400 an orphan by ending a line with an operator that is the start of the next line. Optimistic updates are probably fastest when values are already set because it knows its already done. You could make it better by using the alias field names so someone in the future will know what a t40ofl is. Select only one field from the exists clause so sql won't have to pull in a whole row.
I am trying to do this simple query, but it does not work. Thanks.
SELECT * FROM TSimple where (start_date < '2012-04-20' and end_date is null) or
(end_date > '2012-04-20' and start_date < '2012-04-20')
class TSimple (models.Model):
start_date = models.DateTimeField()
end_date = models.DateTimeField(blank=True, null=True)
...
class TSimpleResource(ModelResource):
def dehydrate(self, bundle):
request_method = bundle.request.META['REQUEST_METHOD']
if request_method=='GET':
new_date = bundle.request.GET.get('new_date', '')
qs = TSimple.objects.raw(
'SELECT * FROM TSimple where (start_date<=\'' +
new_date + '\' and end_date>=\'' +
new_date + '\') or (start_date<=\'' + new_date +
'\' and end_date is null)')
ret_list = [row for row in qs]
// NOT WORK. Not able to get correct json data in javascript.
// It needs return bundle. HOW to replace bundle?
// Is this correct way to do it?
return ret_list
else:
// This is ok.
return bundle
I have following questions:
1) (raw sql method) If implementing in dehydrate method is correct way to do it? If it is, above does not work. It should return bundle object. How to construct new bundle?
If above method is ok, I noticed that bundle already constructed .data field with default query(?), which will be thrown away with new query. That raise the questions if this is right way to do it.
2) If there are other raw sql method to do it? Where to execute the sql?
3) How to do it in filter?
4) I know sql and not familiar with complex filter. That's why I am trying to use raw sql method to do quick prototype. What are the draw back? I noticed that using Tastypie has many unnecessary queries which I don't know how to get rid of it. Example, query on table with foreign key trigger query to another table's data, which I don't want to get.
I figure out the filter and it seems worked. But I am still interested in raw sql.
def apply_filters(self, request, applicable_filters):
base_filter = super(TSimpleResource, self).apply_filters(request,
applicable_filters)
new_date = request.GET.get('new_date', None)
if new_date:
qset = (
(
Q(start_date__lte=new_date) &
Q(end_date__gte=new_date)
) |
(
Q(start_date__lte=new_date) &
Q(end_date__isnull=True)
)
)
base_filter = base_filter.filter(qset)
return base_filter
I'm writing a web app in Perl using Dancer framework. The database is in sqlite and I use DBI for database interaction.
I'm fine with select statements, but I wonder is there a way to count selected rows.
E.g. I have
get '/' => sub {
my $content = database->prepare(sprintf("SELECT * FROM content LIMIT %d",
$CONTNUM));
$content->execute;
print(Dumper($content->fetchall_arrayref));
};
How do I count all items in the result without issuing another query?
What I want to achieve this way is showing 30 items per page and knowing how many pages there would be. Of course I can run SELECT COUNT (*) foo bar, but it looks wrong and redundant to me. I'm looking for a more or less general, DRY and not too heavy on database way to do so.
Any SQL or Perl hack or a hint what should I read about would be appreciated.
// I know using string concatenation for querys is bad
You have to do it the hard way: one query to get the count and another to get your desired slice of the row set:
my $count = $database->prepare('SELECT COUNT(*) FROM content');
$count->execute();
my $n = $count->fetchall_arrayref()->[0][0];
my $content = $database->prepare('SELECT * FROM content LIMIT ?');
$content->execute($CONTNUM);
#...
Not too familiar with perl, but I assume you can just store the result of $content->fetchall_arrayref and retrieve the count from that array befor you print it.
[edit]
Something like
my $ref = $content->fetchall_arrayref;
my $count = scalar(#$ref);
Don't use sqlite myself but the following might work:
select * from table join (select count(*) from table);
Whether the above works or not the first thing I'd look for is scrollable cursors if you are going to page through results - I doubt sqlite has those. However, in DBI you can use fetchall_arrayref with a max_rows to fetch a "page" at a time. Just look up the example in the DBI docs under fetchall_arrayref - it is something like this:
my $rowcache = [];
while( my $row = ( shift(#$rowcache) || shift(#{$rowcache=$sth->fetchall_arrayref(undef,100)||[]}) )
) {
# do something here
}
UPDATE: Added what you'd get with selectall_hashref assuming the table is called content with one integer column called "a":
$ perl -le 'use DBI; my $h = DBI->connect("dbi:SQLite:dbname=fred.db"); my $r = $h->selectall_hashref(q/select * from content join (select count(*) as count from content)/, "a");use Data::Dumper;print Dumper($r);'
$VAR1 = {
'1' => {
'count' => '3',
'a' => '1'
},
'3' => {
'count' => '3',
'a' => '3'
},
'2' => {
'count' => '3',
'a' => '2'
}
};
If you want to know how many results there will be, as well as getting the results themselves, all in one query, then get the count as a new value:
SELECT COUNT(*) AS num_rows, * from Table WHERE ...
Now the row count will be the first column of every row of your resultset, so simply pop that off before presenting the data.
Could some tell me if there is a function which works the same as PHP's mysql_real_escape_string() for Perl from the DBI module?
You should use placeholders and bind values.
Don't. Escape. SQL.
Don't. Quote. SQL.
Use SQL placeholders/parameters (?). The structure of the SQL statement and the data values represented by the placeholders are sent to the database completely separately, so (barring a bug in the database engine or the DBD module) there is absolutely no way that the data values can be interpreted as SQL commands.
my $name = "Robert'); DROP TABLE Students; --";
my $sth = $dbh->prepare('SELECT id, age FROM Students WHERE name = ?');
$sth->execute($name); # Finds Little Bobby Tables without harming the db
As a side benefit, using placeholders is also more efficient if you re-use your SQL statement (it only needs to be prepared once) and no less efficient if you don't (if you don't call prepare explicitly, it still gets called implicitly before the query is executed).
Like quote?
I would also recommend reading the documentation for DBD::MySQL if you are worried about utf8.
From http://www.stonehenge.com/merlyn/UnixReview/col58.html :
use SQL::Abstract;
...
my $sqa = SQL::Abstract->new;
my ($owner, $account_type) = #_; # from inputs
my ($sql, #bind) = $sqa->select('account_data', # table
[qw(account_id balance)], # fields
{
account_owner => $owner,
account_type => $account_type
}, # "where"
);
my $sth = $dbh->prepare_cached($sql); # reuse SQL if we can
$sth->execute(#bind); # execute it for this query
Database Handle Method "quote"
my $dbh = DBI->connect( ... );
$sql = sprintf "SELECT foo FROM bar WHERE baz = %s",
$dbh->quote("Don't");
http://metacpan.org/pod/DBI#quote