NAME

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

DESCRIPTION

This module generates SQL from Perl data structures. It is a subclass of SQL::Abstract::Classic or SQL::Abstract, fully compatible with the parent class, but with some improvements :

methods take arguments as named parameters instead of positional parameters. This is more flexible for identifying and assembling various SQL clauses, like -where, -order_by, -group_by, etc.
additional SQL constructs like -union, -group_by, join, with recursive, etc. are supported
WHERE .. IN clauses can range over multiple columns (tuples)
values passed to select, insert or update can directly incorporate information about datatypes, in the form of arrayrefs of shape [{dbd_attrs => \%type}, $value]
several SQL dialects can adapt the generated SQL to various DBMS vendors

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.

Unfortunately, this module cannot be used with DBIx::Class, because DBIx::Class creates its own instance of SQL::Abstract and has no API to let the client instantiate from any other class.

SYNOPSIS

use SQL::Abstract::More;                             # will inherit from SQL::Abstract::Classic;
#or
use SQL::Abstract::More -extends => 'SQL::Abstract'; # will inherit from SQL::Abstract;

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;

# ex5: multicolumns-in
$sqla = SQL::Abstract::More->new(
  multicols_sep        => '/',
  has_multicols_in_SQL => 1,
);
($sql, @bind) = $sqla->select(
 -from     => 'Foo',
 -where    => {"foo/bar/buz" => {-in => ['1/a/X', '2/b/Y', '3/c/Z']}},
);

# ex6: merging several criteria
my $merged = $sqla->merge_conditions($cond_A, $cond_B, ...);
($sql, @bind) = $sqla->select(..., -where => $merged, ..);

# ex7: insert / update / delete
($sql, @bind) = $sqla->insert(
  -add_sql => 'OR IGNORE',        # SQLite syntax
  -into    => $table,
  -values  => {col => $val, ...},
);
($sql, @bind) = $sqla->insert(
  -into    => $table,
  -columns => [qw/a b/],
  -select  => {-from => 'Bar', -columns => [qw/x y/], -where => ...},
);
($sql, @bind) = $sqla->update(
  -table => $table,
  -set   => {col => $val, ...},
  -where => \%conditions,
);
($sql, @bind) = $sqla->delete (
  -from  => $table
  -where => \%conditions,
);

# ex8 : initial WITH clause -- example borrowed from https://sqlite.org/lang_with.html
($sql, @bind) = $sqla->with_recursive(
  [ -table     => 'parent_of',
    -columns   => [qw/name parent/],
    -as_select => {-columns => [qw/name mom/],
                   -from    => 'family',
                   -union   => [-columns => [qw/name dad/], -from => 'family']},
   ],

  [ -table     => 'ancestor_of_alice',
    -columns   => [qw/name/],
    -as_select => {-columns   => [qw/parent/],
                   -from      => 'parent_of',
                   -where     => {name => 'Alice'},
                   -union_all => [-columns => [qw/parent/],
                                  -from    => [qw/-join parent_of {name} ancestor_of_alice/]],
               },
   ],
  )->select(
   -columns  => 'family.name',
   -from     => [qw/-join ancestor_of_alice {name} family/],
   -where    => {died => undef},
   -order_by => 'born',
  );

CLASS METHODS

import

The import() method is called automatically when a client writes use SQL::Abstract::More.

At this point there is a choice to make about the class to inherit from. Originally this module was designed as an extension of SQL::Abstract in its versions prior to 1.81. Then SQL::Abstract was rewritten with a largely different architecture, published under v2.000001. A fork of the previous version is now published under SQL::Abstract::Classic. SQL::Abstract::More can inherit from either version; initially it used SQL::Abstract as the default parent, but now the default is back to SQL::Abstract::Classic for better compatibility with previous behaviours (see for example https://rt.cpan.org/Ticket/Display.html?id=143837).

The choice of the parent class is made according to the following rules :

SQL::Abstract::Classic is the default parent.
another parent can be specified through the -extends keyword:
```
use SQL::Abstract::More -extends => 'SQL::Abstract';
```

Classic is a shorthand to SQL::Abstract::Classic

use SQL::Abstract::More -extends => 'Classic';

If the environment variable SQL_ABSTRACT_MORE_EXTENDS is defined, its value is used as an implicit -extends

BEGIN {$ENV{SQL_ABSTRACT_MORE_EXTENDS} = 'Classic';
       use SQL::Abstract::More; # will inherit from SQL::Abstract::Classic;
      }

Multiple calls to import() must all resolve to the same parent; otherwise an exception is raised.

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 (?, ?)) )

multicols_sep

A string or compiled regular expression used as a separator for "multicolumns". This separator can then be used on the left-hand side and right-hand side of an IN operator, like this :

my $sqla = SQL::Abstract::More->new(multicols_sep => '/');
($sql, @bind) = $sqla->select(
 -from     => 'Foo',
 -where    => {"x/y/z" => {-in => ['1/A/foo', '2/B/bar']}},
);

Alternatively, tuple values on the right-hand side can also be given as arrayrefs instead of plain scalars with separators :

-where    => {"x/y/z" => {-in => [[1, 'A', 'foo'], [2, 'B', 'bar']]}},

but the left-hand side must stay a plain scalar because an array reference wouldn't be a proper key for a Perl hash; in addition, the presence of the separator in the string is necessary to trigger the special algorithm for multicolumns.

The generated SQL depends on the boolean flag has_multicols_in_SQL, as explained in the next paragraph.

has_multicols_in_SQL

A boolean flag that controls which kind of SQL will be generated for multicolumns. If the flag is true, this means that the underlying DBMS supports multicolumns in SQL, so we just generate tuple expressions. In the example from the previous paragraph, the SQL and bind values would be :

# $sql  : "WHERE (x, y, z) IN ((?, ?, ?), (?, ?, ?))"
# @bind : [ qw/1 A foo 2 B bar/ ]

It is also possible to use a subquery, like this :

($sql, @bind) = $sqla->select(
 -from     => 'Foo',
 -where    => {"x/y/z" => {-in => \[ 'SELECT (a, b, c) FROM Bar '
                                     . 'WHERE a > ?', 99]}},
);
# $sql  : "WHERE (x, y, z) IN (SELECT (a, b, c) FROM Bar WHERE a > ?)"
# @bind : [ 99 ]

If the flag is false, the condition on tuples will be automatically converted using boolean logic :

# $sql  : "WHERE (   (x = ? AND y = ? AND z = ?) 
                  OR (x = ? AND y = ? AND z = ?))"
# @bind : [ qw/1 A foo 2 B bar/ ]

If the flag is false, subqueries are not allowed.

select_implicitly_for

A value that will be automatically added as a -for clause in calls to "select". This default clause can always be overridden by an explicit -for in a given select :

my $sqla = SQL::Abstract->new(-select_implicitly_for => 'READ ONLY');
($sql, @bind) = $sqla->select(-from => 'Foo');
  # SELECT * FROM FOO FOR READ ONLY
($sql, @bind) = $sqla->select(-from => 'Foo', -for => 'UPDATE');
  # SELECT * FROM FOO FOR UPDATE
($sql, @bind) = $sqla->select(-from => 'Foo', -for => undef);
  # SELECT * FROM FOO

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. If "quote_char" in SQL::Abstract is defined, aliased columns will be quoted, unless they contain parentheses, in which case they are considered as SQL expressions for which the user should handle the quoting himself. For example if quote_char is "`",

-columns => [ qw/foo.bar|fb length(buz)|lbuz/ ]

will produce

SELECT `foo`.`bar` AS fb, length(buz) AS lbuz

and not

SELECT `foo`.`bar` AS fb, length(`buz`) AS lbuz

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. In most cases this is used together with a GROUP BY clause. This is like a -where clause, except that the criteria are applied after grouping has occurred.

-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,
  -add_sql   => $keyword,
);

# insert from a subquery
($sql, @bind) = $sqla->insert(
  -into    => $destination_table,
  -columns => \@columns_into
  -select  => {-from => $source_table, -columns => \@columns_from, -where => ...},
);

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

Parameters -into and -values are passed verbatim to the parent method.

Parameters -select and -columns are used for selecting from subqueries -- this is incompatible with the -values parameter.

Parameter -returning is optional and only supported by some database vendors (see "insert" in SQL::Abstract); if the $return_structure is

a scalar or an arrayref, it is passed directly to the parent method
a hashref, it is interpreted as a SQL clause "RETURNING .. INTO ..", as required in particular by Oracle. Hash keys are field names, and hash values are references to variables that will receive the results. Then it is the client code's responsibility to use "bind_param_inout" in DBD::Oracle for binding the variables and retrieving the results, but the "bind_params" method in the present module is there for help. Example:
```
($sql, @bind) = $sqla->insert(
  -into      => $table,
  -values    => {col => $val, ...},
  -returning => {key_col => \my $generated_key},
);

my $sth = $dbh->prepare($sql);
$sqla->bind_params($sth, @bind);
$sth->execute;
print "The new key is $generated_key";
```

Optional parameter -add_sql is used with some specific SQL dialects, for injecting additional SQL keywords after the INSERT keyword. Examples :

$sqla->insert(..., -add_sql => 'IGNORE')     # produces "INSERT IGNORE ..."    -- MySQL
$sqla->insert(..., -add_sql => 'OR IGNORE')  # produces "INSERT OR IGNORE ..." -- SQLite

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,
  -returning => $return_structure,
  -add_sql   => $keyword,
);

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.

Optional parameter -returning works like for the "insert" method.

Optional parameter -add_sql is used with some specific SQL dialects, for injecting additional SQL keywords after the UPDATE keyword. Examples :

$sqla->update(..., -add_sql => 'IGNORE')     # produces "UPDATE IGNORE ..."    -- MySQL
$sqla->update(..., -add_sql => 'OR IGNORE')  # produces "UPDATE OR IGNORE ..." -- SQLite

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,
  -add_sql  => $keyword,
);

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.

Optional parameter -add_sql is used with some specific SQL dialects, for injecting additional SQL keywords after the DELETE keyword. Examples :

$sqla->delete(..., -add_sql => 'IGNORE')     # produces "DELETE IGNORE ..."    -- MySQL
$sqla->delete(..., -add_sql => 'OR IGNORE')  # produces "DELETE OR IGNORE ..." -- SQLite

with_recursive, with

my $new_sqla = $sqla->with_recursive( # or: $sqla->with(

  [ -table     => $CTE_table_name,
    -columns   => \@CTE_columns,
    -as_select => \%select_args ],

  [ -table     => $CTE_table_name2,
    -columns   => \@CTE_columns2,
    -as_select => \%select_args2 ],
  ...

 );
 ($sql, @bind) = $new_sqla->insert(...);

# or, if there is only one table expression
my $new_sqla = $sqla->with_recursive(
    -table     => $CTE_table_name,
    -columns   => \@CTE_columns,
    -as_select => \%select_args,
   );

Returns a new instance with an encapsulated common table expression (CTE), i.e. a kind of local view that can be used as a table name for the rest of the SQL statement -- see https://en.wikipedia.org/wiki/Hierarchical_and_recursive_queries_in_SQL for an explanation of such expressions, or, if you are using Oracle, see the documentation for so-called subquery factoring clauses in SELECT statements.

Further calls to select, insert, update and delete on that new instance will automatically prepend a WITH or WITH RECURSIVE clause before the usual SQL statement.

Arguments to with_recursive() are expressed as a list of arrayrefs; each arrayref corresponds to one table expression, with the following named parameters :

-table

The name to be assigned to the table expression

-columns

An optional list of column aliases to be assigned to the columns resulting from the internal select

-as_select

The implementation of the table expression, given as a hashref of arguments following the same syntax as the "select" method.

-final_clause

An optional SQL clause that will be added after the table expression. This may be needed for example for an Oracle cycle clause, like

($sql, @bind) = $sqla->with_recursive(
  -table        => ...,
  -as_select    => ...,
  -final_clause => "CYCLE x SET is_cycle TO '1' DEFAULT '0'",
 )->select(...);

If there is only one table expression, its arguments can be passed directly as an array instead of a single arrayref.

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',
'>=<' => '%s FULL OUTER JOIN %s ON %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. For example the DBIx::DataModel ORM uses hashrefs for communicating with SQL::Abstract::More.

joins with USING clause instead of ON

In most DBMS, when column names on both sides of a join are identical, the join can be expressed as

SELECT * FROM T1 INNER JOIN T2 USING (A, B)

instead of

SELECT * FROM T1 INNER JOIN T2 ON T1.A=T2.A AND T1.B=T2.B

The advantage of this syntax with a USING clause is that the joined columns will appear only once in the results, and they do not need to be prefixed by a table name if they are needed in the select list or in the WHERE part of the SQL.

To express joins with the USING syntax in SQL::Abstract::More, just mention the column names within curly braces, without any equality operator. For example

->join(qw/Table1 {a,b} Table2 {c} Table3/)

will generate

SELECT * FROM Table1 INNER JOIN Table2 USING (a,b)
                     INNER JOIN Table3 USING (c)

In this case the internal hashref representation has the following shape :

{
  operator  => '<=>',
  using     => [ 'a', 'b'],
}

When they are generated directy by the client code, internal hashrefs must have either a condition field or a using field; it is an error to have both.

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:

if the value is a scalarref, call
```
$sth->bind_param_inout($index, $value, $INOUT_MAX_LEN)
```
(see "bind_param_inout" in DBI). $INOUT_MAX_LEN defaults to 99, which should be good enough for most uses; should you need another value, you can change it by setting
```
local $SQL::Abstract::More::INOUT_MAX_LEN = $other_value;
```
if the value is an arrayref that matches "is_bind_value_with_type", then call the method and arguments returned by "is_bind_value_with_type".
for all other cases, call
```
$sth->bind_param($index, $value);
```

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] :

if %args is of shape {dbd_attrs => \%sql_type}, then return ('bind_param', $orig_value, \%sql_type).
if %args is of shape {sqlt_size => $num}, then return ('bind_param_inout', $orig_value, $num).

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.

UTILITY FUNCTIONS

shallow_clone

my $clone = SQL::Abstract::More::shallow_clone($some_object, %override);

Returns a shallow copy of the object passed as argument. A new hash is created with copies of the top-level keys and values, and it is blessed into the same class as the original object. Not to be confused with the full recursive copy performed by "clone" in Clone.

The optional %override hash is also copied into $clone; it can be used to add other attributes or to override existing attributes in $some_object.

does()

if (SQL::Abstract::More::does $ref, 'ARRAY') {...}

Very cheap version of a does() method, that checks whether a given reference can act as an ARRAY, HASH, SCALAR or CODE. This was designed for the limited internal needs of this module and of DBIx::DataModel; for more complete implementations of a does() method, see Scalar::Does, UNIVERSAL::DOES or Class::DOES.

AUTHOR

Laurent Dami, <laurent dot dami at cpan dot org>

ACKNOWLEDGEMENTS

https://github.com/rouzier : support for -having without -order_by

SUPPORT

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

perldoc SQL::Abstract::More

The same documentation is also available at https://metacpan.org/module/SQL::Abstract::More

LICENSE AND COPYRIGHT

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.

To install SQL::Abstract::More, copy and paste the appropriate command in to your terminal.

cpanm

cpanm SQL::Abstract::More

CPAN shell

perl -MCPAN -e shell
install SQL::Abstract::More

For more information on module installation, please visit the detailed CPAN module installation guide.

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