Laurent Dami > SQL-Abstract-More-1.23 > SQL::Abstract::More

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NAME ^

SQL::Abstract::More - extension of SQL::Abstract with more constructs and more flexible API

DESCRIPTION ^

Generates SQL from Perl data structures. This is a subclass of SQL::Abstract, fully compatible with the parent class, but with some additions :

This module was designed for the specific needs of DBIx::DataModel, but is published as a standalone distribution, because it may possibly be useful for other needs.

SYNOPSIS ^

  my $sqla = SQL::Abstract::More->new();
  my ($sql, @bind);

  # ex1: named parameters, select DISTINCT, ORDER BY, LIMIT/OFFSET
  ($sql, @bind) = $sqla->select(
   -columns  => [-distinct => qw/col1 col2/],
   -from     => 'Foo',
   -where    => {bar => {">" => 123}},
   -order_by => [qw/col1 -col2 +col3/],  # BY col1, col2 DESC, col3 ASC
   -limit    => 100,
   -offset   => 300,
  );

  # ex2: column aliasing, join
  ($sql, @bind) = $sqla->select(
    -columns => [         qw/Foo.col_A|a           Bar.col_B|b /],
    -from    => [-join => qw/Foo           fk=pk   Bar         /],
  );

  # ex3: INTERSECT (or similar syntax for UNION)
  ($sql, @bind) = $sqla->select(
    -columns => [qw/col1 col2/],
    -from    => 'Foo',
    -where   => {col1 => 123},
    -intersect => [ -columns => [qw/col3 col4/],
                    -from    => 'Bar',
                    -where   => {col3 => 456},
                   ],
  );

  # ex4: passing datatype specifications
  ($sql, @bind) = $sqla->select(
   -from     => 'Foo',
   -where    => {bar => [{dbd_attrs => {ora_type => ORA_XMLTYPE}}, $xml]},
  );
  my $sth = $dbh->prepare($sql);
  $sqla->bind_params($sth, @bind);
  $sth->execute;

  # merging several criteria
  my $merged = $sqla->merge_conditions($cond_A, $cond_B, ...);
  ($sql, @bind) = $sqla->select(..., -where => $merged, ..);

  # insert / update / delete
  ($sql, @bind) = $sqla->insert(
    -into   => $table,
    -values => {col => $val, ...},
  );
  ($sql, @bind) = $sqla->update(
    -table => $table,
    -set   => {col => $val, ...},
    -where => \%conditions,
  );
  ($sql, @bind) = $sqla->delete (
    -from  => $table
    -where => \%conditions,
  );

CLASS METHODS ^

new

  my $sqla = SQL::Abstract::More->new(%options);

where %options may contain any of the options for the parent class (see "new" in SQL::Abstract), plus the following :

table_alias

A sprintf format description for generating table aliasing clauses. The default is %s AS %s. Can also be supplied as a method coderef (see "Overriding methods").

column_alias

A sprintf format description for generating column aliasing clauses. The default is %s AS %s. Can also be supplied as a method coderef.

limit_offset

Name of a "limit-offset dialect", which can be one of LimitOffset, LimitXY, LimitYX or RowNum; see SQL::Abstract::Limit for an explanation of those dialects. Here, unlike the SQL::Abstract::Limit implementation, limit and offset values are treated as regular values, with placeholders '?' in the SQL; values are postponed to the @bind list.

The argument can also be a coderef (see below "Overriding methods"). That coderef takes $self, $limit, $offset as arguments, and should return ($sql, @bind). If $sql contains %s, it is treated as a sprintf format string, where the original SQL is injected into %s.

join_syntax

A hashref where keys are abbreviations for join operators to be used in the "join" method, and values are associated SQL clauses with placeholders in sprintf format. The default is described below under the "join" method.

join_assoc_right

A boolean telling if multiple joins should be associative on the right or on the left. Default is false (i.e. left-associative).

max_members_IN

An integer specifying the maximum number of members in a "IN" clause. If the number of given members is greater than this maximum, SQL::Abstract::More will automatically split it into separate clauses connected by 'OR' (or connected by 'AND' if used with the -not_in operator).

  my $sqla = SQL::Abstract::More->new(max_members_IN => 3);
  ($sql, @bind) = $sqla->select(
   -from     => 'Foo',
   -where    => {foo => {-in     => [1 .. 5]}},
                 bar => {-not_in => [6 .. 10]}},
  );
  # .. WHERE (     (foo IN (?,?,?) OR foo IN (?, ?))
  #            AND (bar NOT IN (?,?,?) AND bar NOT IN (?, ?)) )
sql_dialect

This is actually a "meta-argument" : it injects a collection of regular arguments, tuned for a specific SQL dialect. Dialects implemented so far are :

MsAccess

For Microsoft Access. Overrides the join syntax to be right-associative.

BasisJDBC

For Livelink Collection Server (formerly "Basis"), accessed through a JDBC driver. Overrides the column_alias syntax. Sets max_members_IN to 255.

MySQL_old

For old versions of MySQL. Overrides the limit_offset syntax. Recent versions of MySQL do not need that because they now implement the regular "LIMIT ? OFFSET ?" ANSI syntax.

Oracle

For Oracle. Overrides the limit_offset to use the "RowNum" dialect (beware, this injects an additional column rownum__index into your resultset). Also sets max_members_IN to 999.

Overriding methods

Several arguments to new() can be references to method implementations instead of plain scalars : this allows you to completely redefine a behaviour without the need to subclass. Just supply a regular method body as a code reference : for example, if you need another implementation for LIMIT-OFFSET, you could write

  my $sqla = SQL::Abstract::More->new(
    limit_offset => sub {
      my ($self, $limit, $offset) = @_;
      defined $limit or die "NO LIMIT!"; #:-)
      $offset ||= 0;
      my $last = $offset + $limit;
      return ("ROWS ? TO ?", $offset, $last); # ($sql, @bind)
     });

INSTANCE METHODS ^

select

  # positional parameters, directly passed to the parent class
  ($sql, @bind) = $sqla->select($table, $columns, $where, $order);

  # named parameters, handled in this class 
  ($sql, @bind) = $sqla->select(
    -columns  => \@columns,
      # OR: -columns => [-distinct => @columns],
    -from     => $table || \@joined_tables,
    -where    => \%where,
    -union    => [ %select_subargs ], # OR -intersect, -minus, etc
    -order_by => \@order,
    -group_by => \@group_by,
    -having   => \%having_criteria,
    -limit => $limit, -offset => $offset,
      # OR: -page_size => $size, -page_index => $index,
    -for      => $purpose,
   );

  my $details = $sqla->select(..., want_details => 1);
  # keys in %$details: sql, bind, aliased_tables, aliased_columns

If called with positional parameters, as in SQL::Abstract, select() just forwards the call to the parent class. Otherwise, if called with named parameters, as in the example above, some additional SQL processing is performed.

The following named arguments can be specified :

-columns => \@columns

\@columns is a reference to an array of SQL column specifications (i.e. column names, * or table.*, functions, etc.).

A '|' in a column is translated into a column aliasing clause: this is convenient when using perl qw/.../ operator for columns, as in

  -columns => [ qw/table1.longColumn|t1lc table2.longColumn|t2lc/ ]

SQL column aliasing is then generated through the "column_alias" method.

Initial items in @columns that start with a minus sign are shifted from the array, i.e. they are not considered as column names, but are re-injected later into the SQL (without the minus sign), just after the SELECT keyword. This is especially useful for

  $sqla->select(..., -columns => [-DISTINCT => @columns], ...);

However, it may also be useful for other purposes, like vendor-specific SQL variants :

   # MySQL features
  ->select(..., -columns => [-STRAIGHT_JOIN    => @columns], ...);
  ->select(..., -columns => [-SQL_SMALL_RESULT => @columns], ...);

   # Oracle hint
  ->select(..., -columns => ["-/*+ FIRST_ROWS (100) */" => @columns], ...);

The argument to -columns can also be a string instead of an arrayref, like for example "c1 AS foobar, MAX(c2) AS m_c2, COUNT(c3) AS n_c3"; however this is mainly for backwards compatibility. The recommended way is to use the arrayref notation as explained above :

  -columns => [ qw/  c1|foobar   MAX(c2)|m_c2   COUNT(c3)|n_c3  / ]

If omitted, -columns takes '*' as default argument.

-from => $table || \@joined_tables
-where => $criteria

Like in SQL::Abstract, $criteria can be a plain SQL string like "col1 IN (3, 5, 7, 11) OR col2 IS NOT NULL"; but in most cases, it will rather be a reference to a hash or array of conditions that will be translated into SQL clauses, like for example {col1 => 'val1', col2 => 'val2'}. The structure of that hash or array can be nested to express complex boolean combinations of criteria; see "WHERE CLAUSES" in SQL::Abstract for a detailed description.

When using hashrefs or arrayrefs, leaf values can be "bind values with types"; see the "BIND VALUES WITH TYPES" section below.

-union => [ %select_subargs ]
-union_all => [ %select_subargs ]
-intersect => [ %select_subargs ]
-except => [ %select_subargs ]
-minus => [ %select_subargs ]

generates a compound query using set operators such as UNION, INTERSECT, etc. The argument %select_subargs contains a nested set of parameters like for the main select (i.e. -columns, -from, -where, etc.); however, arguments -columns and -from can be omitted, in which case they will be copied from the main select(). Several levels of set operators can be nested.

-group_by => "string" or -group_by => \@array

adds a GROUP BY clause in the SQL statement. Grouping columns are specified either by a plain string or by an array of strings.

-having => "string" or -having => \%criteria

adds a HAVING clause in the SQL statement (only makes sense together with a GROUP BY clause). This is like a -where clause, except that the criteria are applied after grouping has occured.

-order_by => \@order

\@order is a reference to a list of columns for sorting. Columns can be prefixed by '+' or '-' for indicating sorting directions, so for example -orderBy => [qw/-col1 +col2 -col3/] will generate the SQL clause ORDER BY col1 DESC, col2 ASC, col3 DESC.

Column names asc and desc are treated as exceptions to this rule, in order to preserve compatibility with SQL::Abstract. So -orderBy => [-desc => 'colA'] yields ORDER BY colA DESC and not ORDER BY desc DEC, colA. Any other syntax supported by SQL::Abstract is also supported here; see "ORDER BY CLAUSES" in SQL::Abstract for examples.

The whole -order_by parameter can also be a plain SQL string like "col1 DESC, col3, col2 DESC".

-page_size => $page_size

specifies how many rows will be retrieved per "page" of data. Default is unlimited (or more precisely the maximum value of a short integer on your system). When specified, this parameter automatically implies -limit.

-page_index => $page_index

specifies the page number (starting at 1). Default is 1. When specified, this parameter automatically implies -offset.

-limit => $limit

limit to the number of rows that will be retrieved. Automatically implied by -page_size.

-offset => $offset

Automatically implied by -page_index. Defaults to 0.

-for => $clause

specifies an additional clause to be added at the end of the SQL statement, like -for => 'READ ONLY' or -for => 'UPDATE'.

-want_details => 1

If true, the return value will be a hashref instead of the usual ($sql, @bind). The hashref contains the following keys :

sql

generated SQL

bind

bind values

aliased_tables

a hashref of {table_alias => table_name} encountered while parsing the -from parameter.

aliased_columns

a hashref of {column_alias => column_name} encountered while parsing the -columns parameter.

insert

  # positional parameters, directly passed to the parent class
  ($sql, @bind) = $sqla->insert($table, \@values || \%fieldvals, \%options);

  # named parameters, handled in this class 
  ($sql, @bind) = $sqla->insert(
    -into      => $table,
    -values    => {col => $val, ...},
    -returning => $return_structure,
  );

Like for "select", values assigned to columns can have associated SQL types; see "BIND VALUES WITH TYPES".

Named parameters to the insert() method are just syntactic sugar for better readability of the client's code. Parameters -into and -values are passed verbatim to the parent method. Parameter -returning is optional and only supported by some database vendors (see "insert" in SQL::Abstract); if the $return_structure is

update

  # positional parameters, directly passed to the parent class
  ($sql, @bind) = $sqla->update($table, \%fieldvals, \%where);

  # named parameters, handled in this class
  ($sql, @bind) = $sqla->update(
    -table    => $table,
    -set      => {col => $val, ...},
    -where    => \%conditions,
    -order_by => \@order,
    -limit    => $limit,
  );

This works in the same spirit as the "insert" method above. Positional parameters are supported for backwards compatibility with the old API; but named parameters should be preferred because they improve the readability of the client's code.

Few DBMS would support parameters -order_by and -limit, but MySQL does -- see http://dev.mysql.com/doc/refman/5.6/en/update.html.

delete

  # positional parameters, directly passed to the parent class
  ($sql, @bind) = $sqla->delete($table, \%where);

  # named parameters, handled in this class 
  ($sql, @bind) = $sqla->delete (
    -from     => $table
    -where    => \%conditions,
    -order_by => \@order,
    -limit    => $limit,

  );

Positional parameters are supported for backwards compatibility with the old API; but named parameters should be preferred because they improve the readability of the client's code.

Few DBMS would support parameters -order_by and -limit, but MySQL does -- see http://dev.mysql.com/doc/refman/5.6/en/update.html.

table_alias

  my $sql = $sqla->table_alias($table_name, $alias);

Returns the SQL fragment for aliasing a table. If $alias is empty, just returns $table_name.

column_alias

Like table_alias, but for column aliasing.

limit_offset

  ($sql, @bind) = $sqla->limit_offset($limit, $offset);

Generates ($sql, @bind) for a LIMIT-OFFSET clause.

join

  my $join_info = $sqla->join(
    <table0> <join_1> <table_1> ... <join_n> <table_n>
  );
  my $sth = $dbh->prepare($join_info->{sql});
  $sth->execute(@{$join_info->{bind}})
  while (my ($alias, $aliased) = each %{$join_info->{aliased_tables}}) {
    say "$alias is an alias for table $aliased";
  }

Generates join information for a JOIN clause, taking as input a collection of joined tables with their join conditions. The following example gives an idea of the available syntax :

  ($sql, @bind) = $sqla->join(qw[
     Table1|t1       ab=cd                     Table2|t2
                 <=>{ef>gh,ij<kl,mn='foobar'}  Table3
                  =>{t1.op=qr}                 Table4
     ]);

This will generate

  Table1 AS t1 INNER JOIN Table2 AS t2 ON t1.ab=t2.cd
               INNER JOIN Table3       ON t2.ef>Table3.gh
                                      AND t2.ij<Table3.kl
                                      AND t2.mn=?
                LEFT JOIN Table4       ON t1.op=Table4.qr

with one bind value foobar.

More precisely, the arguments to join() should be a list containing an odd number of elements, where the odd positions are table specifications and the even positions are join specifications.

Table specifications

A table specification for join is a string containing the table name, possibly followed by a vertical bar and an alias name. For example Table1 or Table1|t1 are valid table specifications.

These are converted into internal hashrefs with keys sql, bind, name, aliased_tables, like this :

  {
    sql            => "Table1 AS t1"
    bind           => [],
    name           => "t1"
    aliased_tables => {"t1" => "Table1"}
  }

Such hashrefs can be passed directly as arguments, instead of the simple string representation.

Join specifications

A join specification is a string containing an optional join operator, possibly followed by a pair of curly braces or square brackets containing the join conditions.

Default builtin join operators are <=>, =>, <=, ==, corresponding to the following SQL JOIN clauses :

  '<=>' => '%s INNER JOIN %s ON %s',
   '=>' => '%s LEFT OUTER JOIN %s ON %s',
  '<='  => '%s RIGHT JOIN %s ON %s',
  '=='  => '%s NATURAL JOIN %s',

This operator table can be overridden through the join_syntax parameter of the "new" method.

The join conditions are a comma-separated list of binary column comparisons, like for example

  {ab=cd,Table1.ef<Table2.gh}

Table names may be explicitly given using dot notation, or may be implicit, in which case they will be filled automatically from the names of operands on the left-hand side and right-hand side of the join.

Strings within quotes will be treated as bind values instead of column names; pairs of quotes within such values become single quotes. Ex.

  {ab=cd,ef='foo''bar',gh<ij}

becomes

  ON Table1.ab=Table2.cd AND Table1.ef=? AND Table1.gh<Table2.ij
  # bind value: "foo'bar"

In accordance with SQL::Abstract common conventions, if the list of comparisons is within curly braces, it will become an AND; if it is within square brackets, it will become an OR.

Join specifications expressed as strings are converted into internal hashrefs with keys operator and condition, like this :

  {
    operator  => '<=>',
    condition => { '%1$s.ab' => {'=' => {-ident => '%2$s.cd'}},
                   '%1$s.ef' => {'=' => {-ident => 'Table2.gh'}}},
  }

The operator is a key into the join_syntax table; the associated value is a sprintf format string, with placeholders for the left and right operands, and the join condition. The condition is a structure suitable for being passed as argument to "where" in SQL::Abstract. Places where the names of left/right tables (or their aliases) are expected should be expressed as sprintf placeholders, i.e. respectively %1$s and %2$s. Usually the right-hand side of the condition refers to a column of the right table; in such case it should not belong to the @bind list, so this is why we need to use the -ident operator from SQL::Abstract. Only when the right-hand side is a string constant (string within quotes) does it become a bind value : for example

  ->join(qw/Table1 {ab=cd,ef='foobar'}) Table2/)

is parsed into

  [ 'Table1',
    { operator  => '<=>',
      condition => { '%1$s.ab' => {'=' => {-ident => '%2$s.cd'}},
                     '%1$s.ef' => {'=' => 'foobar'} },
    },
    'Table2',
  ]

Hashrefs for join specifications as shown above can be passed directly as arguments, instead of the simple string representation.

Return value

The structure returned by join() is a hashref with the following keys :

sql

a string containing the generated SQL

bind

an arrayref of bind values

aliased_tables

a hashref where keys are alias names and values are names of aliased tables.

merge_conditions

  my $conditions = $sqla->merge_conditions($cond_A, $cond_B, ...);

This utility method takes a list of "where" conditions and merges all of them in a single hashref. For example merging

  ( {a => 12, b => {">" => 34}}, 
    {b => {"<" => 56}, c => 78} )

produces

  {a => 12, b => [-and => {">" => 34}, {"<" => 56}], c => 78});

bind_params

  $sqla->bind_params($sth, @bind);

For each $value in @bind:

This method is useful either as a convenience for Oracle statements of shape "INSERT ... RETURNING ... INTO ..." (see "insert" method above), or as a way to indicate specific datatypes to the database driver.

is_bind_value_with_type

  my ($method, @args) = $sqla->is_bind_value_with_type($value);

If $value is a ref to a pair [\%args, $orig_value] :

Otherwise, return ().

BIND VALUES WITH TYPES ^

At places where SQL::Abstract would expect a plain value, SQL::Abstract::More also accepts a pair, i.e. an arrayref of 2 elements, where the first element is a type specification, and the second element is the value. This is convenient when the DBD driver needs additional information about the values used in the statement.

The usual type specification is a hashref {dbd_attrs => \%type}, where \%type is passed directly as third argument to "bind_param" in DBI, and therefore is specific to the DBD driver.

Another form of type specification is {sqlt_size => $num}, where $num will be passed as buffer size to "bind_param_inout" in DBI.

Here are some examples

  ($sql, @bind) = $sqla->insert(
   -into   => 'Foo',
   -values => {bar => [{dbd_attrs => {ora_type => ORA_XMLTYPE}}]},
  );
  ($sql, @bind) = $sqla->select(
   -from  => 'Foo',
   -where => {d_begin => {">" => [{dbd_attrs => {ora_type => ORA_DATE}}, 
                                  $some_date]}},
  );

When using this feature, the @bind array will contain references that cannot be passed directly to DBI methods; so you should use "bind_params" from the present module to perform the appropriate bindings before executing the statement.

TODO ^

Future versions may include some of these features :

AUTHOR ^

Laurent Dami, <laurent.dami at justice.ge.ch>

BUGS ^

Please report any bugs or feature requests to bug-sql-abstract-more at rt.cpan.org, or through the web interface at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=SQL-Abstract-More. I will be notified, and then you'll automatically be notified of progress on your bug as I make changes.

SUPPORT ^

You can find documentation for this module with the perldoc command.

    perldoc SQL::Abstract::More

You can also look for information at:

RT: CPAN's request tracker

http://rt.cpan.org/NoAuth/Bugs.html?Dist=SQL-Abstract-More

AnnoCPAN: Annotated CPAN documentation

http://annocpan.org/dist/SQL-Abstract-More

CPAN Ratings

http://cpanratings.perl.org/d/SQL-Abstract-More

MetaCPAN

https://metacpan.org/module/SQL::Abstract::More

LICENSE AND COPYRIGHT ^

Copyright 2011, 2012 Laurent Dami.

This program is free software; you can redistribute it and/or modify it under the terms of either: the GNU General Public License as published by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.

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