(Perl) Create query for DBI with SQL::Abstract - sql

I want to add new record to table1 on SQLite
use SQL::Abstract;
my %data = (
id => \'max(id)', # it is doesn't work so which variant is right?
record => 'Something'
);
my $sql = SQL::Abstract->new;
my ($stmt, #bind) = $sql->insert('table1', \%data);
...
my $sth = $dbh->prepare($stmt);
If I used DBIx::Class in Catalyst app I would written like so:
id => $c->model('Model')->get_column('id')->max()
and it will work fine.
So how can I reach the same aim but using just SQL::Abstract which is used in DBIx::Class as well.
Could someone fixed it? Thanks.

This is a piece of code. As you can see, first you need to get the max id+1 and then do the insert command. I have to notice you this is not safe, because in a multi-(user,process,thread) environment, a second process can execute the same code and get race conditions.
But I assume you are just learning the SQL::Abstract api, and that problem doesn't matter
use DBI;
use SQL::Abstract;
#create table TEST(ID integer, NAME varchar);
my $dbh = DBI->connect('dbi:SQLite:dbname=test.db', '', '', {AutoCommit=>1});
my $sql = SQL::Abstract->new;
my($stmt, #bind) = $sql->select("TEST", [ 'max(ID)+1 as ID' ] );
my $sth = $dbh->prepare($stmt);
$sth->execute(#bind);
my ($id) = $sth->fetchrow_array // 1;
print "Select ID: $id", "\n";
$sth->finish;
($stmt, #bind) = $sql->insert("TEST", { ID=>$id, NAME=>"test-name"} );
$sth = $dbh->prepare($stmt);
$sth->execute(#bind);
$dbh->disconnect;

Related

Can Laravel automatically switch between column = ? and column IS NULL depending on value?

When building a complex SQL query for Laravel, using ? as placeholders for parameters is great. However when the value is null, the SQL syntax needs to be changed from = ? to IS NULL. Plus, since the number of parameters is one less, I need to pass a different array.
To get it to work, I have written it like this, but there must be a better way:
if ($cohortId === null) {
// sql should be: column IS NULL
$sqlCohortString = "IS NULL";
$params = [
Carbon::today()->subDays(90),
// no cohort id here
];
} else {
// sql should be: column = ?
$sqlCohortString = "= ?";
$params = [
Carbon::today()->subDays(90),
$cohortId
];
}
$query = "SELECT items.`name`,
snapshots.`value`,
snapshots.`taken_at`,
FROM snapshots
INNER JOIN (
SELECT MAX(id) AS id, item_id
FROM snapshots
WHERE `taken_at` > ?
AND snapshots.`cohort_id` $sqlCohortString
GROUP BY item_id
) latest
ON latest.`id` = snapshots.`id`
INNER JOIN items
ON items.`id` = snapshots.`item_id`
ORDER by media_items.`slug` ASC
";
$chartData = DB::select($query, $params);
My question is: does Laravel have a way to detect null values and replace ? more intelligently?
PS: The SQL is for a chart, so I need the single highest snapshot value for each item.
You can use ->when to create a conditional where clause:
$data = DB::table('table')
->when($cohortId === null, function ($query) {
return $query->whereNull('cohort_id');
}, function ($query) use ($cohortId) {
// the "use" keyword provides access to "outer" variables
return $query->where('cohort_id', '=', $cohortId);
})
->where('taken_at', '>', $someDate)
->toSql();

Perl SQL::Parser table alias substitution: works for SELECT column names but not for WHERE column names

I'm trying to parse some SQL queries stored in a log database -- I don't want to submit them to a SQL database, just to extract the fields used in the SELECT and WHERE clause.
I've been fiddling with several SQL parsers in Java, Python and Perl. The one that seems to work better for my problem are SQL::Parser and SQL::Statement. With those I was able to write the following code:
#!/usr/bin/perl
use strict;
use SQL::Parser;
use SQL::Statement;
use Data::Dumper;
my $sql = "SELECT sl.plate,sp.fehadop FROM sppLines AS sl ".
"JOIN sppParams AS sp ON sl.specobjid = sp.specobjid ".
"WHERE fehadop < -3.5 ";
my $parser = SQL::Parser->new();
my $stmt = SQL::Statement->new($sql,$parser);
printf("COMMAND [%s]\n",$stmt->command);
printf("COLUMNS \n");
my #columns = #{$stmt->column_defs()};
foreach my $column ( #columns)
{
print " ".$column->{value}."\n";
}
printf("TABLES \n");
my #tables = $stmt->tables();
foreach my $table ( #tables)
{
print " ".$table->{name}."\n";
}
printf("WHERE COLUMNS\n");
my $where_hash = $stmt->where_hash();
print Dumper($where_hash);
Sorry if it is too long, it is the smallest, self-contained example I could devise.
The output of this code is:
COMMAND [SELECT]
COLUMNS
spplines.plate
sppparams.fehadop
TABLES
spplines
sppparams
WHERE COLUMNS
$VAR1 = {
'arg1' => {
'value' => 'fehadop',
'type' => 'column',
'fullorg' => 'fehadop'
},
'op' => '<',
'nots' => {},
'arg2' => {
'str' => '-?0?',
'fullorg' => '-3.5',
'name' => 'numeric_exp',
'value' => [
{
'fullorg' => '3.5',
'value' => '3.5',
'type' => 'number'
}
],
'type' => 'function'
},
'neg' => 0
};
The parser returns the name of columns (obtained through a call to $stmt->column_defs()) already renamed with the real tables names (e.g. spplines.plate instead of s1.plate) -- this is what I want.
I also want the names of the columns used in the WHERE clause.
I already know how to recursively parse the results of $stmt->where_hash() (didn't include the code to make the post clear), but even from dumping its contents I can see that the column names are not associated with the tables.
I would like to ensure that the columns names in the WHERE clause are also preceded by the tables name. After parsing the results of $stmt->where_hash() I would get sppparams.fehadop instead of fehadop.
Is this possible with SQL::Parser?
Thanks
(big edit -- tried to make the question clearer)
Since SQL::Statement has an eval_where, I suspect there might be a better way, but you can try a function like this:
get_column($stmt->column_defs(), $where_hash->{arg1});
sub get_column {
my ($columns, $arg) = #_;
return $arg->{fullorg} if ($arg->{type} ne 'column');
foreach my $col (#$columns) {
return $col->{value} if ($col->{fullorg} eq $arg->{fullorg});
my ($name) = ( $col->{fullorg} =~ /([^.]+)$/);
return $col->{value} if ($name eq $arg->{fullorg});
}
return $arg->{fullorg};
}

ZF2: Is there a more efficient way to do this Zend\Db Update query?

Here's some ZF1 code for an update query:
$this->getAdapter()->update(
'users', $data, $this->getAdapter()->quoteInto('node_id = ?', $user->nodeId)
);
Here's the same query with ZF2:
$param = $this->getAdapter()->platform->quoteValue($user->nodeId);
$sqlOj = new Sql($this->getAdapter());
$update = $sqlOj->update('users')->set($data)->where('node_id = ' . $param);
$updateString = $sqlOj->getSqlStringForSqlObject($update);
$this->getAdapter()->query($updateString, Adapter::QUERY_MODE_EXECUTE);
As you can see, one line of ZF1 code has become 5 lines of ZF2 code, (actually without the fluent interface it would be 7 lines...)
Am I missing something? Or is ZF2's DB component just more verbose that ZF1?
BTW, I have found the same scenario with select and insert queries too...
I managed to limit it to 3 lines.
use \Zend\Db\Sql\Sql;
$sql = new Sql ($adapter);
$update = $sql->update ('users')->set ($data)->where (['id = ?' => 1]);
$adapter->query ($sql->getSqlStringForSqlObject ($update), $db::QUERY_MODE_EXECUTE);
The problem is they didn't expect you to run your updates like that. Instead, you are expected to use a table gateway.
This way it becomes one line again:
$this->tableGateway->update($data, array('id' => $id));

How to generate list of tables for DB using RoseDB

I have to list the tables for a given database using RoseDB . I know the mysql command for it :
SHOW TABLES in DB_NAME;
How do I implement this in rose DB ? Pleas help
It's not really a Rose::DB-specific question. Simply use the database handle how you would normally in DBI:
package My::DB {
use Rose::DB;
our #ISA = qw(Rose::DB);
My::DB->register_db(
domain => 'dev',
type => 'main',
driver => 'mysql',
...
);
My::DB->default_domain('dev');
My::DB->default_type('main');
}
use Carp;
my $db = My::DB->new();
my $sth = $db->dbh->prepare('SHOW TABLES');
$sth->execute || croak "query failed";
while (my $row = $sth->fetchrow_arrayref) {
print "$row->[0]\n";
}

How to output JSON from recordset in Dreamweaver with minimal manual code? [duplicate]

I have a basic MySQL database table People with 3 columns (ID, Name, Distance)
I am trying to output this with PHP as a JSON so my web app can pick it up. I tried using the solution from another answer:
$sth = mysql_query($con,"SELECT * FROM People");
$rows = array();
while($r = mysql_fetch_assoc($sth)) {
$rows[] = $r;
}
print json_encode($rows);
However I am just returning a blank array of [].
Update: Changed to mysqli and added dumps:
$sth = mysqli_query("SELECT * FROM Events",$con);
$rows = array();
var_dump($sth);
while($r = mysqli_fetch_assoc($sth)) {
var_dump($rows);
$rows[] = $r;
}
print json_encode($rows);
Returns:
NULL []
Swap your query and connection in the mysql_query-statement:
$sth = mysql_query("SELECT * FROM People", $con);
Besides that, the mysql-library is deprecated. If you're writing new code consider using mysqli_ or PDO.
Why no mysql_connect ?
var_dump($sth); // check the return of mysql_query()
var_dump($rows); // check the array of mysql_fetch_assoc result
I would check if your query is returning any rows first.
<?php
$rows = array();
array_push($rows, array("name" => "John"));
array_push($rows, array("name" => "Jack"));
array_push($rows, array("name" => "Peter"));
print json_encode($rows);
?>
Produces this output.
[{"name":"John"},{"name":"Jack"},{"name":"Peter"}]
Solved using a combination of answer to get:
$sth = mysqli_query($con,"SELECT * FROM Events");
$datarray = array();
while($row = mysqli_fetch_assoc($sth)) {
$datarray[] = $row;
}
print_r(json_encode($datarray));