Data::ObjectDriver::SQUser Contributed Perl DocumentData::ObjectDriver::SQL(3)NAMEData::ObjectDriver::SQL - an SQL statement
SYNOPSIS
my $sql = Data::ObjectDriver::SQL->new();
$sql->select([ 'id', 'name', 'bucket_id', 'note_id' ]);
$sql->from([ 'foo' ]);
$sql->add_where('name', 'fred');
$sql->add_where('bucket_id', { op => '!=', value => 47 });
$sql->add_where('note_id', \'IS NULL');
$sql->limit(1);
my $sth = $dbh->prepare($sql->as_sql);
$sth->execute(@{ $sql->{bind} });
my @values = $sth->selectrow_array();
my $obj = SomeObject->new();
$obj->set_columns(...);
DESCRIPTIONData::ObjectDriver::SQL represents an SQL statement. SQL statements are
used internally to "Data::ObjectDriver::Driver::DBI" object drivers to
convert database operations ("search()", "update()", etc) into database
operations, but sometimes you just gotta use SQL.
ATTRIBUTESData::ObjectDriver::SQL sports several data attributes that represent
the parts of the modeled SQL statement. These attributes all have
accessor and mutator methods. Note that some attributes have more
convenient methods of modification (for example, "add_where()" for the
"where" attribute).
"select" (arrayref)
The database columns to select in a "SELECT" query.
"distinct" (boolean)
Whether the "SELECT" query should return DISTINCT rows only.
"select_map" (hashref)
The map of database column names to object fields in a "SELECT" query.
Use this mapping to convert members of the "select" list to column
names.
"select_map_reverse" (hashref)
The map of object fields to database column names in a "SELECT" query.
Use this map to reverse the "select_map" mapping where needed.
"from" (arrayref)
The list of tables from which to query results in a "SELECT" query.
Note if you perform a "SELECT" query with multiple tables, the rows
will be selected as Cartesian products that you'll need to reduce with
"WHERE" clauses. Your query might be better served with real joins
specified through the "joins" attribute of your statement.
"joins" (arrayref of hashrefs containing scalars and hashrefs)
The list of "JOIN" clauses to use in the table list of the statement.
Each clause is a hashref containing these members:
· "table"
The name of the table in "from" being joined.
· "joins" (arrayref)
The list of joins to perform on the table named in "table". Each
member of "joins" is a hashref containing:
· "type"
The type of join to use. That is, the SQL string to use before
the word "JOIN" in the join expression; for example, "INNER" or
"NATURAL RIGHT OUTER"). This member is optional. When not
specified, the default plain "JOIN" join is specified.
· "table"
The name of the table to which to join.
· "condition"
The SQL expression across which to perform the join, as a
string.
"where" (arrayref)
The list of "WHERE" clauses that apply to the SQL statement. Individual
members of the list are strings of SQL. All members of this attribute
must be true for a record to be included as a result; that is, the list
members are "AND"ed together to form the full "WHERE" clause.
"where_values" (hashref of variant structures)
The set of data structures used to generate the "WHERE" clause SQL
found in the "where" attributes, keyed on the associated column names.
"bind" (arrayref)
The list of values to bind to the query when performed. That is, the
list of values to be replaced for the "?"es in the SQL.
"limit" (scalar)
The maximum number of results on which to perform the query.
"offset" (scalar)
The number of records to skip before performing the query. Combined
with a "limit" and application logic to increase the offset in
subsequent queries, you can paginate a set of records with a moving
window containing "limit" records.
"group" (hashref, or an arrayref of hashrefs)
The fields on which to group the results. Grouping fields are hashrefs
containing these members:
· "column"
Name of the column on which to group.
Note you can set a single grouping field, or use an arrayref containing
multiple grouping fields.
"having" (arrayref)
The list of clauses to specify in the "HAVING" portion of a "GROUP ...
HAVING" clause. Individual clauses are simple strings containing the
conditional expression, as in "where".
"order" (hashref, or an arrayref of hashrefs)
Returns or sets the fields by which to order the results. Ordering
fields are hashrefs containing these members:
· "column"
Name of the column by which to order.
· "desc"
The SQL keyword to use to specify the ordering. For example, use
"DESC" to specify a descending order. This member is optional.
Note you can set a single ordering field, or use an arrayref containing
multiple ordering fields.
"$sql->comment([ $comment ])"
Returns or sets a simple comment to the SQL statement
USAGE
"Data::ObjectDriver::SQL->new()"
Creates a new, empty SQL statement.
"$sql->add_select($column [, $term ])"
Adds the database column $column to the list of fields to return in a
"SELECT" query. The requested object member will be indicated to be
$term in the statement's "select_map" and "select_map_reverse"
attributes.
$term is optional, and defaults to the same value as $column.
"$sql->add_join($table, \@joins)"
Adds the join statement indicated by $table and "\@joins" to the list
of "JOIN" table references for the statement. The structure for the set
of joins are as described for the "joins" attribute member above.
"$sql->add_index_hint($table, $index)"
Specifies a particular index to use for a particular table.
"$sql->add_where($column, $value)"
Adds a condition on the value of the database column $column to the
statement's "WHERE" clause. A record will be tested against the below
conditions according to what type of data structure $value is:
· a scalar
The value of $column must equal $value.
· a reference to a scalar
The value of $column must evaluate true against the SQL given in
$$value. For example, if $$value were "IS NULL", $column must be
"NULL" for a record to pass.
· a hashref
The value of $column must compare against the condition represented
by $value, which can contain the members:
· "value"
The value with which to compare (required).
· "op"
The SQL operator with which to compare "value" and the value of
$column (required).
· "column"
The column name for the comparison. If this is present, it
overrides the column name $column, allowing you to build more
complex conditions like "((foo = 1 AND bar = 2) OR (baz = 3))".
For example, if "value" were "NULL" and "op" were "IS", a record's
$column column would have to be "NULL" to match.
· an arrayref of scalars
The value of $column may equal any of the members of @$value. The
generated SQL performs the comparison with as an "IN" expression.
· an arrayref of (mostly) references
The value of $column must compare against any of the expressions
represented in @$value. Each member of the list can be any of the
structures described here as possible forms of $value.
If the first member of the @$value array is the scalar string
"-and", all subsequent members of <@$value> must be met for the
record to match. Note this is not very useful unless contained as
one option of a larger "OR" alternation.
All individual conditions specified with "add_where()" must be true for
a record to be a result of the query.
Beware that you can create a circular reference that will recursively
generate an infinite SQL statement (for example, by specifying a
arrayref $value that itself contains $value). As "add_where()"
evaluates your expressions before storing the conditions in the "where"
attribute as a generated SQL string, this will occur when calling
"add_where()", not "as_sql()". So don't do that.
"$sql->add_complex_where(\@list)"
This method accepts an array reference of clauses that are glued
together with logical operators. With it, you can express where clauses
that mix logical operators together to produce more complex queries.
For instance:
[ { foo => 1, bar => 2 }, -or => { baz => 3 } ]
The values given for the columns support all the variants documented
for the "add_where()" method above. Logical operators used inbetween
the hashref elements can be one of: '-or', '-and', '-or_not',
'-and_not'.
"$sql->has_where($column, [$value])"
Returns whether a where clause for the column $column was added to the
statement with the "add_where()" method.
The $value argument is currently ignored.
"$sql->add_having($column, $value)"
Adds an expression to the "HAVING" portion of the statement's "GROUP
... HAVING" clause. The expression compares $column using $value,
which can be any of the structures described above for the
"add_where()" method.
"$sql->add_index_hint($table, \@hints)"
Addes the index hint into a "SELECT" query. The structure for the set
of "\@hints" are arrayref of hashrefs containing these members:
· "type" (scalar)
The name of the type. "USE", "IGNORE or "FORCE".
· "list" (arrayref)
The list of name of indexes which to use.
"$sql->as_sql()"
Returns the SQL fully representing the SQL statement $sql.
"$sql->as_sql_having()"
Returns the SQL representing the "HAVING" portion of $sql's "GROUP ...
HAVING" clause.
"$sql->as_sql_where()"
Returns the SQL representing $sql's "WHERE" clause.
"$sql->as_limit()"
Returns the SQL for the "LIMIT ... OFFSET" clause of the statement.
"$sql->as_aggregate($set)"
Returns the SQL representing the aggregation clause of type $set for
the SQL statement $sql. Reasonable values of $set are "ORDER" and
"GROUP".
DIAGNOSTICS
· "Invalid/unsafe column name column"
The column name you specified to "add_where()" contained characters
that are not allowed in database column names. Only word characters
and periods are allowed. Perhaps you didn't filter punctuation out
of a generated column name correctly.
BUGS AND LIMITATIONSData::ObjectDriver::SQL does not provide the functionality for turning
SQL statements into instances of object classes.
SEE ALSOLICENSE
Data::ObjectDriver is free software; you may redistribute it and/or
modify it under the same terms as Perl itself.
AUTHOR & COPYRIGHT
Except where otherwise noted, Data::ObjectDriver is Copyright 2005-2006
Six Apart, cpan@sixapart.com. All rights reserved.
perl v5.14.1 2010-03-22 Data::ObjectDriver::SQL(3)
