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Diffstat (limited to 'odb-examples/view/employee.hxx')
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diff --git a/odb-examples/view/employee.hxx b/odb-examples/view/employee.hxx new file mode 100644 index 0000000..5add690 --- /dev/null +++ b/odb-examples/view/employee.hxx @@ -0,0 +1,350 @@ +// file : view/employee.hxx +// copyright : not copyrighted - public domain + +#ifndef EMPLOYEE_HXX +#define EMPLOYEE_HXX + +#include <string> +#include <memory> // std::shared_ptr +#include <cstddef> // std::size_t + +#include <odb/core.hxx> +#include <odb/nullable.hxx> + +#pragma db object +class country +{ +public: + country (const std::string& code, const std::string& name) + : code_ (code), name_ (name) + { + } + + const std::string& + name () const + { + return name_; + } + +private: + friend class odb::access; + + country () {} + + #pragma db id + std::string code_; // ISO 2-letter country code. + + std::string name_; +}; + +#pragma db object +class employer +{ +public: + employer (unsigned long id, const std::string& name) + : id_ (id), name_ (name) + { + } + + const std::string& + name () const + { + return name_; + } + +private: + friend class odb::access; + + employer () {} + + #pragma db id + unsigned long id_; + + std::string name_; +}; + +#pragma db object +class employee +{ +public: + employee (unsigned long id, + const std::string& first, + const std::string& last, + unsigned short age, + std::shared_ptr<country> res, + std::shared_ptr<country> nat, + std::shared_ptr<employer> e) + : id_ (id), first_ (first), last_ (last), age_ (age), + residence_ (res), + nationality_ (nat), + employed_by_ (e) + { + } + + // Name. + // + const std::string& + first () const + { + return first_; + } + + const std::string& + last () const + { + return last_; + } + + // Age. + // + unsigned short + age () const + { + return age_; + } + + // Employer. + // + std::shared_ptr<employer> + employed_by () const + { + return employed_by_; + } + + // Residence and nationality. + // + std::shared_ptr<country> + residence () const + { + return residence_; + } + + std::shared_ptr<country> + nationality () const + { + return nationality_; + } + +private: + friend class odb::access; + + employee () {} + + #pragma db id + unsigned long id_; + + std::string first_; + std::string last_; + + unsigned short age_; + + std::shared_ptr<country> residence_; + std::shared_ptr<country> nationality_; + + std::shared_ptr<employer> employed_by_; +}; + +// We also have the "legacy" employee_extra table that is not mapped to any +// persistent class. It has the following columns: +// +// CREATE TABLE employee_extra( +// employee_id INTEGER NOT NULL, +// vacation_days INTEGER NOT NULL, +// previous_employer_id INTEGER) +// + +// A simple view with a single associated object. It allows us to get +// the name of an employee without loading any of the other parts, such +// as the referenced country and employer objects. The first and last +// data members in the view are automatically associated to the first_ +// and last_ members in the employee object. +// +#pragma db view object(employee) +struct employee_name +{ + std::string first; + std::string last; +}; + +// A simple aggregate view. It allows us to count the number of employees +// matching certain criteria. Here we use a column expression with a +// reference to the id_ data member in the employee object. +// +#pragma db view object(employee) +struct employee_count +{ + #pragma db column("count(" + employee::id_ + ")") + std::size_t count; +}; + +// A simple view with two associated object. It allows us to get the +// name of an employee and its employer without loading any other parts. +// Because there is an unambiguous relationship between the employee and +// employer objects (employee::employed_by_), the ODB compiler is able to +// automatically use this relationship as a join condition. Also, similar +// to the employee_name view, the first and last data members are auto- +// associated to the first_ and last_ members in the employee object. +// For the employer_name member we provide an explicit member reference. +// +#pragma db view object(employee) object(employer) +struct employee_employer +{ + std::string first; + std::string last; + + #pragma db column(employer::name_) + std::string employer_name; +}; + +// A more interesting aggregate view that uses the GROUP BY clause. It +// allows us to calculate the min/max ages of employees for each employer. +// Here we use the query condition with a placeholder (?). +// +#pragma db view object(employee) object(employer) \ + query ((?) + "GROUP BY" + employer::name_) +struct employer_age +{ + #pragma db column(employer::name_) + std::string employer_name; + + #pragma db column("min(" + employee::age_ + ")") + unsigned short min_age; + + #pragma db column("max(" + employee::age_ + ")") + unsigned short max_age; +}; + +// A more complex view with three associated objects, two of which are +// of the same type. This requires us to use aliases and disambiguate +// the relationships used to associate each object. +// +#pragma db view object(employee) \ + object(country = res_country: employee::residence_) \ + object(country = nat_country: employee::nationality_) +struct employee_country +{ + std::string first; + std::string last; + + #pragma db column(res_country::name_) + std::string res_country_name; + + #pragma db column(nat_country::name_) + std::string nat_country_name; +}; + +// An example of an object loading view. It is a different version of +// the above view that loads the complete objects instead of a subset +// of their data members. +// +#pragma db view object(employee) \ + object(country = res: employee::residence_) \ + object(country = nat: employee::nationality_) +struct employee_country_objects +{ + std::shared_ptr<employee> e; + std::shared_ptr<country> res; + std::shared_ptr<country> nat; +}; + +// An example of using inner join type. Here we want to find employers +// that have any employees. If we were to use the default left join type, +// then we would have gotten all the employers, regardless of whether +// they have any employees. By using the inner join, we make sure that +// only matching employers are returned. +// +// It is also likely that there will be more than one employee for any +// particular employer which will lead to duplicate employer records +// being returned. To avoid this we use the 'distinct' result modifier. +// +// Try to change the join type or remove 'distinct' to observe the +// change in behavior. +// +#pragma db view object(employer) object(employee inner) query(distinct) +struct employer_with_employees +{ + std::shared_ptr<employer> e; +}; + +// An example of a native view that provides a complete query and is based +// on an ad-hoc table. This view allows us to load the employee vacation +// information from the legacy employee_extra table. +// +#ifndef ODB_DATABASE_ORACLE + #pragma db view query("SELECT employee_id, vacation_days " \ + "FROM view_employee_extra") +#else + #pragma db view query("SELECT \"employee_id\", \"vacation_days\" " \ + "FROM \"view_employee_extra\"") +#endif +struct employee_vacation +{ + #pragma db type("INTEGER") + unsigned long id; + + #pragma db type("INTEGER") + unsigned short days; +}; + +// A more robust implementation of the above view as a table view instead +// of a native view. +// +#pragma db view table("view_employee_extra") +struct employee_vacation1 +{ + #pragma db column("employee_id") type("INTEGER") + unsigned long id; + + #pragma db column("vacation_days") type("INTEGER") + unsigned short days; +}; + +// An improved version of the previous view that extracts the employee +// first and last names instead of the id. To get the names we need to +// add the employee object to this view and use a custom join condition +// to tie it up with our legacy table. +// +#ifndef ODB_DATABASE_ORACLE + #pragma db view table("view_employee_extra") \ + object(employee: "view_employee_extra.employee_id = " + employee::id_) +#else + #pragma db view table("view_employee_extra") \ + object(employee: "\"view_employee_extra\".\"employee_id\" = " + \ + employee::id_) +#endif +struct employee_vacation2 +{ + std::string first; + std::string last; + + #pragma db column("view_employee_extra.vacation_days") type("INTEGER") + unsigned short days; +}; + +// A mixed view that associates two objects and a legacy table. It returns +// the previous employer information for each employee. +// +#ifndef ODB_DATABASE_ORACLE + #pragma db view object(employee) \ + table("view_employee_extra" = "extra": \ + "extra.employee_id = " + employee::id_) \ + object(employer: "extra.previous_employer_id = " + employer::id_) +#else + #pragma db view object(employee) \ + table("view_employee_extra" = "extra": \ + "\"extra\".\"employee_id\" = " + employee::id_) \ + object(employer: "\"extra\".\"previous_employer_id\" = " + employer::id_) +#endif +struct employee_prev_employer +{ + std::string first; + std::string last; + + // If previous_employer_id is NULL, then the name will be NULL as well. + // We use the odb::nullable wrapper to handle this. + // + #pragma db column(employer::name_) + odb::nullable<std::string> prev_employer_name; +}; + +#endif // EMPLOYEE_HXX |