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1 | =head1 NAME |
2 | |
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3 | DBIx::Class::Manual::Intro - Introduction to DBIx::Class |
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4 | |
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5 | =head1 INTRODUCTION |
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6 | |
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7 | So, you are bored with SQL, and want a native Perl interface for your |
8 | database? Or you've been doing this for a while with L<Class::DBI>, |
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9 | and think there's a better way? You've come to the right place. |
10 | Let's look at how you can set and use your first native L<DBIx::Class> |
11 | tree. |
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12 | |
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13 | First we'll see how you can set up your classes yourself. If you want |
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14 | them to be auto-discovered, just skip to the next section, which shows |
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15 | you how to use L<DBIx::Class::Schema::Loader>. |
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16 | |
17 | =head2 Setting it up manually |
18 | |
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19 | First, you should create your base schema class, which inherits from |
20 | L<DBIx::Class::Schema>: |
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21 | |
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22 | package My::Schema; |
23 | use base qw/DBIx::Class::Schema/; |
24 | |
25 | In this class you load your result_source ("table", "model") classes, which |
26 | we will define later, using the load_classes() method. You can specify which |
27 | classes to load manually: |
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28 | |
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29 | # load My::Schema::Album and My::Schema::Artist |
30 | __PACKAGE__->load_classes(qw/ Album Artist /); |
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31 | |
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32 | Or load classes by namespace: |
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33 | |
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34 | # load My::Schema::Album, My::Schema::Artist and My::OtherSchema::LinerNotes |
35 | __PACKAGE__->load_classes( |
36 | { |
37 | 'My::Schema' => [qw/ Album Artist /], |
38 | 'My::OtherSchema' => [qw/ LinerNotes /] |
39 | } |
40 | ); |
41 | |
42 | Or let your schema class load all classes in its namespace automatically: |
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43 | |
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44 | # load My::Schema::* |
45 | __PACKAGE__->load_classes(); |
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46 | |
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47 | Next, create each of the classes you want to load as specified above: |
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48 | |
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49 | package My::Schema::Album; |
50 | use base qw/DBIx::Class/; |
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51 | |
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52 | Load any components required by each class with the load_components() method. |
53 | This should consist of "Core" plus any additional components you want to use. |
54 | For example, if you want serial/auto-incrementing primary keys: |
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55 | |
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56 | __PACKAGE__->load_components(qw/ PK::Auto Core /); |
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57 | |
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58 | C<PK::Auto> is supported for many databases; see |
59 | L<DBIx::Class::Storage::DBI> for more information. |
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60 | |
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61 | Set the table for your class: |
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62 | |
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63 | __PACKAGE__->table('album'); |
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64 | |
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65 | Add columns to your class: |
66 | |
67 | __PACKAGE__->add_columns(qw/ albumid artist title /); |
68 | |
69 | Each column can also be set up with its own accessor, data_type and other |
70 | pieces of information that it may be useful to have, just pass C<add_columns> |
71 | a hash such as: |
72 | |
73 | __PACKAGE__->add_columns(albumid => |
74 | { accessor => 'album', |
75 | data_type => 'integer', |
76 | size => 16, |
77 | is_nullable => 0, |
78 | is_auto_increment => 1, |
79 | default_value => '', |
80 | }, |
81 | artist => |
82 | { data_type => 'integer', |
83 | size => 16, |
84 | is_nullable => 0, |
85 | is_auto_increment => 0, |
86 | default_value => '', |
87 | }, |
88 | title => |
89 | { data_type => 'varchar', |
90 | size => 256, |
91 | is_nullable => 0, |
92 | is_auto_increment => 0, |
93 | default_value => '', |
94 | } |
95 | ); |
96 | |
97 | Most of this data isn't yet used directly by DBIx::Class, but various related |
98 | modules such as L<DBIx::Class::WebForm> make use of it. Also it allows you |
99 | to create your database tables from your Schema, instead of the other way |
100 | around. See L<SQL::Translator> for details. |
101 | |
102 | See L<DBIx::Class::ResultSource> for more details of the possible column |
103 | attributes. |
104 | |
105 | Accessors are created for each column automatically, so My::Schema::Album will |
106 | have albumid() (or album(), when using the accessor), artist() and title() |
107 | methods. |
108 | |
109 | Define a primary key for your class: |
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110 | |
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111 | __PACKAGE__->set_primary_key('albumid'); |
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112 | |
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113 | If you have a multi-column primary key, just pass a list instead: |
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114 | |
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115 | __PACKAGE__->set_primary_key( qw/ albumid artistid / ); |
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116 | |
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117 | Define relationships that the class has with any other classes by using |
118 | either C<belongs_to> to describe a column which contains an ID of another |
119 | table, or C<has_many> to make a predefined accessor for fetching objects |
120 | that contain this tables foreign key in one of their columns: |
121 | |
122 | __PACKAGE__->has_many('albums', 'My::Schema::Artist', 'album_id'); |
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123 | |
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124 | More information about the various types of relationships available, and |
125 | how you can design your own, can be found in L<DBIx::Class::Relationship>. |
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126 | |
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127 | |
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128 | =head2 Using L<DBIx::Class::Schema::Loader> |
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129 | |
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130 | This is an external module, and not part of the L<DBIx::Class> |
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131 | distribution. Like L<Class::DBI::Loader>, it inspects your database, |
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132 | and automatically creates classes for all the tables in your database. |
133 | Here's a simple setup: |
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134 | |
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135 | package MyApp::DB; |
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136 | use DBIx::Class::Schema::Loader; |
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137 | |
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138 | my $loader = DBIx::Class::Loader->new( |
139 | dsn => 'dbi:SQLite:/home/me/myapp/my.db', |
140 | namespace => 'MyApp::DB' |
141 | ); |
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142 | |
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143 | 1; |
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144 | |
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145 | This should be equivalent to the manual setup in the section above. |
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146 | L<DBIx::Class::Schema::Loader> takes lots of other options. For more |
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147 | information, consult its documentation. |
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148 | |
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149 | =head2 Connecting |
150 | |
151 | L<DBIx::Class::Schema::Loader> already contains the connection info for the |
152 | database, so to get started all you need to do is create an instance of your |
153 | class: |
154 | |
155 | my $schema = MyApp::DB->new(); |
156 | |
157 | To connect to your manually created Schema, you also need to provide the |
158 | connection details: |
159 | |
160 | my $schema = My::Schema->connect('dbi:SQLite:/home/me/myapp/my.db'); |
161 | |
162 | You can create as many different schema instances as you need. So if you have |
163 | a second database you want to access: |
164 | |
165 | my $other_schema = My::Schema->connect( $dsn, $user, $password, $attrs ); |
166 | |
167 | Note that L<DBIx::Class::Schema> does not cache connnections for you. If you |
168 | use multiple connections, you need to do this manually. |
169 | |
170 | To execute some sql statements on every connect you can pass them to your schema after the connect: |
171 | |
172 | $schema->storage->on_connect_do(\@on_connect_sql_statments); |
173 | |
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174 | =head2 Basic usage |
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175 | |
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176 | Once you've defined the basic classes, either manually or using |
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177 | L<DBIx::Class::Schema::Loader>, you can start interacting with your database. |
178 | |
179 | To access your database using your $schema object, you can fetch a L<DBIx::Class::Manual::Glossary/"ResultSet"> |
180 | representing each of your tables by calling the ->resultset method. |
181 | |
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182 | The simplest way to get a record is by primary key: |
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183 | |
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184 | my $album = $schema->resultset('Album')->find(14); |
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185 | |
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186 | This will run a C<SELECT> with C<albumid = 14> in the C<WHERE> clause, |
187 | and return an instance of C<MyApp::DB::Album> that represents this |
188 | row. Once you have that row, you can access and update columns: |
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189 | |
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190 | $album->title('Physical Graffiti'); |
191 | my $title = $album->title; # $title holds 'Physical Graffiti' |
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192 | |
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193 | If you prefer, you can use the C<set_column> and C<get_column> |
194 | accessors instead: |
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195 | |
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196 | $album->set_column('title', 'Presence'); |
197 | $title = $album->get_column('title'); |
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198 | |
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199 | Just like with L<Class::DBI>, you call C<update> to commit your |
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200 | changes to the database: |
201 | |
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202 | $album->update; |
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203 | |
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204 | If needed, you can throw away your local changes like this: |
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205 | |
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206 | $album->discard_changes if $album->is_changed; |
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207 | |
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208 | As you can see, C<is_changed> allows you to check if there are local |
209 | changes to your object. |
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210 | |
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211 | =head2 Adding and removing rows |
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212 | |
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213 | To create a new record in the database, you can use the C<create> |
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214 | method. It returns an instance of C<MyApp::DB::Album> that can be |
215 | used to access the data in the new record: |
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216 | |
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217 | my $new_album = $schema->resultset('Album')->create({ |
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218 | title => 'Wish You Were Here', |
219 | artist => 'Pink Floyd' |
220 | }); |
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221 | |
222 | Now you can add data to the new record: |
223 | |
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224 | $new_album->label('Capitol'); |
225 | $new_album->year('1975'); |
226 | $new_album->update; |
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227 | |
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228 | Likewise, you can remove it from the database like this: |
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229 | |
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230 | $new_album->delete; |
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231 | |
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232 | You can also remove records without retrieving them first, by calling |
233 | delete directly on a ResultSet object. |
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234 | |
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235 | # Delete all of Falco's albums |
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236 | $schema->resultset('Album')->search({ artist => 'Falco' })->delete; |
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237 | |
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238 | =head2 Finding your objects |
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239 | |
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240 | L<DBIx::Class> provides a few different ways to retrieve data from |
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241 | your database. Here's one example: |
242 | |
243 | # Find all of Santana's albums |
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244 | my $rs = $schema->resultset('Album')->search({ artist => 'Santana' }); |
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245 | |
246 | In scalar context, as above, C<search> returns a |
247 | L<DBIx::Class::ResultSet> object. It can be used to peek at the first |
248 | album returned by the database: |
249 | |
250 | my $album = $rs->first; |
251 | print $album->title; |
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252 | |
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253 | You can loop over the albums and update each one: |
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254 | |
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255 | while (my $album = $rs->next) { |
256 | print $album->artist . ' - ' . $album->title; |
257 | $album->year(2001); |
258 | $album->update; |
259 | } |
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260 | |
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261 | Or, you can update them all at once: |
262 | |
263 | $rs->update({ year => 2001 }); |
264 | |
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265 | For more information on what you can do with a |
266 | L<DBIx::Class::ResultSet>, see L<DBIx::Class::ResultSet/METHODS>. |
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267 | |
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268 | In list context, the C<search> method returns all of the matching |
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269 | rows: |
270 | |
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271 | # Fetch immediately all of Carlos Santana's albums |
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272 | my @albums = $schema->resultset('Album')->search( |
273 | { artist => 'Carlos Santana' } |
274 | ); |
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275 | foreach my $album (@albums) { |
276 | print $album->artist . ' - ' . $album->title; |
277 | } |
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278 | |
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279 | We also provide a handy shortcut for doing a C<LIKE> search: |
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280 | |
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281 | # Find albums whose artist starts with 'Jimi' |
282 | my $rs = MyApp::DB::Album->search_like({ artist => 'Jimi%' }); |
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283 | |
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284 | Or you can provide your own C<WHERE> clause, like: |
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285 | |
286 | # Find Peter Frampton albums from the year 1986 |
287 | my $where = 'artist = ? AND year = ?'; |
288 | my @bind = ( 'Peter Frampton', 1986 ); |
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289 | my $rs = $schema->resultset('Album')->search_literal( $where, @bind ); |
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290 | |
291 | The preferred way to generate complex queries is to provide a |
292 | L<SQL::Abstract> construct to C<search>: |
293 | |
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294 | my $rs = $schema->resultset('Album')->search({ |
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295 | artist => { '!=', 'Janis Joplin' }, |
296 | year => { '<' => 1980 }, |
297 | albumid => [ 1, 14, 15, 65, 43 ] |
298 | }); |
299 | |
300 | This results in something like the following C<WHERE> clause: |
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301 | |
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302 | WHERE artist != 'Janis Joplin' |
303 | AND year < 1980 |
304 | AND albumid IN (1, 14, 15, 65, 43) |
305 | |
306 | For more examples of complex queries, see |
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307 | L<DBIx::Class::Manual::Cookbook>. |
308 | |
309 | The search can also be modified by passing another hash with |
310 | attributes: |
311 | |
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312 | my @albums = MyApp::DB::Album->search( |
313 | { artist => 'Bob Marley' }, |
314 | { rows => 2, order_by => 'year DESC' } |
315 | ); |
316 | |
317 | C<@albums> then holds the two most recent Bob Marley albums. |
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318 | |
319 | For a complete overview of the available attributes, see |
320 | L<DBIx::Class::ResultSet/ATTRIBUTES>. |
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321 | |
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322 | =head1 SEE ALSO |
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323 | |
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324 | =over 4 |
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325 | |
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326 | =item * L<DBIx::Class::Manual::Cookbook> |
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327 | |
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328 | =item * L<DBIx::Class::Manual::FAQ> |
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329 | |
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330 | =back |
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331 | |
332 | =cut |