/**
 * Implements hook_views_data().
 */
function {{ machine_name }}_views_data() {
  // This example describes how to write hook_views_data() for a table defined
  // like this:
  // CREATE TABLE example_table (
  //   nid INT(11) NOT NULL         COMMENT 'Primary key: {node}.nid.',
  //   plain_text_field VARCHAR(32) COMMENT 'Just a plain text field.',
  //   numeric_field INT(11)        COMMENT 'Just a numeric field.',
  //   boolean_field INT(1)         COMMENT 'Just an on/off field.',
  //   timestamp_field INT(8)       COMMENT 'Just a timestamp field.',
  //   langcode VARCHAR(12)         COMMENT 'Language code field.',
  //   PRIMARY KEY(nid)
  // );

  // Define the return array.
  $data = [];

  // The outermost keys of $data are Views table names, which should usually
  // be the same as the hook_schema() table names.
  $data['example_table'] = [];

  // The value corresponding to key 'table' gives properties of the table
  // itself.
  $data['example_table']['table'] = [];

  // Within 'table', the value of 'group' (translated string) is used as a
  // prefix in Views UI for this table's fields, filters, etc. When adding
  // a field, filter, etc. you can also filter by the group.
  $data['example_table']['table']['group'] = t('Example table');

  // Within 'table', the value of 'provider' is the module that provides schema
  // or the entity type that causes the table to exist. Setting this ensures
  // that views have the correct dependencies. This is automatically set to the
  // module that implements hook_views_data().
  $data['example_table']['table']['provider'] = 'example_module';

  // Some tables are "base" tables, meaning that they can be the base tables
  // for views. Non-base tables can only be brought in via relationships in
  // views based on other tables. To define a table to be a base table, add
  // key 'base' to the 'table' array:
  $data['example_table']['table']['base'] = [
    // Identifier (primary) field in this table for Views.
    'field' => 'nid',
    // Label in the UI.
    'title' => t('Example table'),
    // Longer description in the UI. Required.
    'help' => t('Example table contains example content and can be related to nodes.'),
    'weight' => -10,
  ];

  // Some tables have an implicit, automatic relationship to other tables,
  // meaning that when the other table is available in a view (either as the
  // base table or through a relationship), this table's fields, filters, etc.
  // are automatically made available without having to add an additional
  // relationship. To define an implicit relationship that will make your
  // table automatically available when another table is present, add a 'join'
  // section to your 'table' section. Note that it is usually only a good idea
  // to do this for one-to-one joins, because otherwise your automatic join
  // will add more rows to the view. It is also not a good idea to do this if
  // most views won't need your table -- if that is the case, define a
  // relationship instead (see below).
  //
  // If you've decided an automatic join is a good idea, here's how to do it;
  // the resulting SQL query will look something like this:
  //   ... FROM example_table et ... JOIN node_field_data nfd
  //   ON et.nid = nfd.nid AND ('extra' clauses will be here) ...
  // although the table aliases will be different.
  $data['example_table']['table']['join'] = [
    // Within the 'join' section, list one or more tables to automatically
    // join to. In this example, every time 'node_field_data' is available in
    // a view, 'example_table' will be too. The array keys here are the array
    // keys for the other tables, given in their hook_views_data()
    // implementations. If the table listed here is from another module's
    // hook_views_data() implementation, make sure your module depends on that
    // other module.
    'node_field_data' => [
      // Primary key field in node_field_data to use in the join.
      'left_field' => 'nid',
      // Foreign key field in example_table to use in the join.
      'field' => 'nid',
      // 'extra' is an array of additional conditions on the join.
      'extra' => [
        0 => [
          // Adds AND node_field_data.published = TRUE to the join.
          'field' => 'published',
          'value' => TRUE,
        ],
        1 => [
          // Adds AND example_table.numeric_field = 1 to the join.
          'left_field' => 'numeric_field',
          'value' => 1,
          // If true, the value will not be surrounded in quotes.
          'numeric' => TRUE,
        ],
        2 => [
          // Adds AND example_table.boolean_field <>
          // node_field_data.published to the join.
          'field' => 'published',
          'left_field' => 'boolean_field',
          // The operator used, Defaults to "=".
          'operator' => '!=',
        ],
      ],
    ],
  ];

  // You can also do a more complex join, where in order to get to a certain
  // base table defined in a hook_views_data() implementation, you will join
  // to a different table that Views knows how to auto-join to the base table.
  // For instance, if another module that your module depends on had
  // defined a table 'foo' with an automatic join to 'node_field_table' (as
  // shown above), you could join to 'node_field_table' via the 'foo' table.
  // Here's how to do this, and the resulting SQL query would look something
  // like this:
  //   ... FROM example_table et ... JOIN foo foo
  //   ON et.nid = foo.nid AND ('extra' clauses will be here) ...
  //   JOIN node_field_data nfd ON (definition of the join from the foo
  //   module goes here) ...
  // although the table aliases will be different.
  $data['example_table']['table']['join']['node_field_data'] = [
    // 'node_field_data' above is the base we're joining to in Views.
    // 'left_table' is the table we're actually joining to, in order to get to
    // 'node_field_data'. It has to be something that Views knows how to join
    // to 'node_field_data'.
    'left_table' => 'foo',
    'left_field' => 'nid',
    'field' => 'nid',
    // 'extra' is an array of additional conditions on the join.
    'extra' => [
      // This syntax matches additional fields in the two tables:
      // ... AND foo.langcode = example_table.langcode ...
      ['left_field' => 'langcode', 'field' => 'langcode'],
      // This syntax adds a condition on our table. 'operator' defaults to
      // '=' for non-array values, or 'IN' for array values.
      // ... AND example_table.numeric_field > 0 ...
      ['field' => 'numeric_field', 'value' => 0, 'numeric' => TRUE, 'operator' => '>'],
    ],
  ];

  // Other array elements at the top level of your table's array describe
  // individual database table fields made available to Views. The array keys
  // are the names (unique within the table) used by Views for the fields,
  // usually equal to the database field names.
  //
  // Each field entry must have the following elements:
  // - title: Translated label for the field in the UI.
  // - help: Description of the field in the UI.
  //
  // Each field entry may also have one or more of the following elements,
  // describing "handlers" (plugins) for the field:
  // - relationship: Specifies a handler that allows this field to be used
  //   to define a relationship to another table in Views.
  // - field: Specifies a handler to make it available to Views as a field.
  // - filter: Specifies a handler to make it available to Views as a filter.
  // - sort: Specifies a handler to make it available to Views as a sort.
  // - argument: Specifies a handler to make it available to Views as an
  //   argument, or contextual filter as it is known in the UI.
  // - area: Specifies a handler to make it available to Views to add content
  //   to the header, footer, or as no result behavior.
  //
  // Note that when specifying handlers, you must give the handler plugin ID
  // and you may also specify overrides for various settings that make up the
  // plugin definition. See examples below; the Boolean example demonstrates
  // setting overrides.

  // Node ID field, exposed as relationship only, since it is a foreign key
  // in this table.
  $data['example_table']['nid'] = [
    'title' => t('Example content'),
    'help' => t('Relate example content to the node content'),

    // Define a relationship to the node_field_data table, so views whose
    // base table is example_table can add a relationship to nodes. To make a
    // relationship in the other direction, you can:
    // - Use hook_views_data_alter() -- see the function body example on that
    //   hook for details.
    // - Use the implicit join method described above.
    'relationship' => [
      // Views name of the table to join to for the relationship.
      'base' => 'node_field_data',
      // Database field name in the other table to join on.
      'base field' => 'nid',
      // ID of relationship handler plugin to use.
      'id' => 'standard',
      // Default label for relationship in the UI.
      'label' => t('Example node'),
    ],
  ];

  // Plain text field, exposed as a field, sort, filter, and argument.
  $data['example_table']['plain_text_field'] = [
    'title' => t('Plain text field'),
    'help' => t('Just a plain text field.'),

    'field' => [
      // ID of field handler plugin to use.
      'id' => 'standard',
    ],

    'sort' => [
      // ID of sort handler plugin to use.
      'id' => 'standard',
    ],

    'filter' => [
      // ID of filter handler plugin to use.
      'id' => 'string',
    ],

    'argument' => [
      // ID of argument handler plugin to use.
      'id' => 'string',
    ],
  ];

  // Numeric field, exposed as a field, sort, filter, and argument.
  $data['example_table']['numeric_field'] = [
    'title' => t('Numeric field'),
    'help' => t('Just a numeric field.'),

    'field' => [
      // ID of field handler plugin to use.
      'id' => 'numeric',
    ],

    'sort' => [
      // ID of sort handler plugin to use.
      'id' => 'standard',
    ],

    'filter' => [
      // ID of filter handler plugin to use.
      'id' => 'numeric',
    ],

    'argument' => [
      // ID of argument handler plugin to use.
      'id' => 'numeric',
    ],
  ];

  // Boolean field, exposed as a field, sort, and filter. The filter section
  // illustrates overriding various settings.
  $data['example_table']['boolean_field'] = [
    'title' => t('Boolean field'),
    'help' => t('Just an on/off field.'),

    'field' => [
      // ID of field handler plugin to use.
      'id' => 'boolean',
    ],

    'sort' => [
      // ID of sort handler plugin to use.
      'id' => 'standard',
    ],

    'filter' => [
      // ID of filter handler plugin to use.
      'id' => 'boolean',
      // Override the generic field title, so that the filter uses a different
      // label in the UI.
      'label' => t('Published'),
      // Override the default BooleanOperator filter handler's 'type' setting,
      // to display this as a "Yes/No" filter instead of a "True/False" filter.
      'type' => 'yes-no',
      // Override the default Boolean filter handler's 'use_equal' setting, to
      // make the query use 'boolean_field = 1' instead of 'boolean_field <> 0'.
      'use_equal' => TRUE,
    ],
  ];

  // Integer timestamp field, exposed as a field, sort, and filter.
  $data['example_table']['timestamp_field'] = [
    'title' => t('Timestamp field'),
    'help' => t('Just a timestamp field.'),

    'field' => [
      // ID of field handler plugin to use.
      'id' => 'date',
    ],

    'sort' => [
      // ID of sort handler plugin to use.
      'id' => 'date',
    ],

    'filter' => [
      // ID of filter handler plugin to use.
      'id' => 'date',
    ],
  ];

  // Area example. Areas are not generally associated with actual data
  // tables and fields. This example is from views_views_data(), which defines
  // the "Global" table (not really a table, but a group of Fields, Filters,
  // etc. that are grouped into section "Global" in the UI). Here's the
  // definition of the generic "Text area":
  $data['views']['area'] = [
    'title' => t('Text area'),
    'help' => t('Provide markup text for the area.'),
    'area' => [
      // ID of the area handler plugin to use.
      'id' => 'text',
    ],
  ];

  return $data;
}
