Статьи

Как извлечь часть даты в SQL

Февраль 10, 2019

Аккаунт Modern SQL Twitter ( от Markus Winand ) опубликовал подсказку о том, как извлечь часть даты в SQL:

Это правда? Да, это так, в стандарте SQL и во множестве совместимых со стандартами баз данных. Но давайте проверим, что делает jOOQ при запуске следующей программы на всех 18 поддерживаемых в настоящее время СУБД

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import static org.jooq.impl.DSL.currentDate;
import static org.jooq.impl.DSL.extract;
import static org.jooq.impl.DSL.using;
 
import java.util.stream.Stream;
 
import org.jooq.DatePart;
import org.jooq.SQLDialect;
 
public class Extract {
    public static void main(String[] args) {
        // Get all distinct SQLDialect families
        Stream
        .of(SQLDialect.values())
        .map(SQLDialect::family)
        .distinct()
        .forEach(family -> {
            System.out.println();
            System.out.println(family);
 
            // Get all supported date parts
            Stream
            .of(DatePart.values())
 
            // For each family / part, get the
            // EXTRACT() function
            .map(part -> extract(currentDate(), part))
            .forEach(expr -> {
                System.out.println(
                    using(family).render(expr)
                );
            });
        });
    }
}

Выход:

Базы данных с открытым исходным кодом

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DEFAULT
extract(year from current_date())
extract(month from current_date())
extract(day from current_date())
extract(hour from current_date())
extract(minute from current_date())
extract(second from current_date())
 
CUBRID
extract(year from current_date())
extract(month from current_date())
extract(day from current_date())
extract(hour from current_date())
extract(minute from current_date())
extract(second from current_date())
 
DERBY
year(current_date)
month(current_date)
day(current_date)
hour(current_date)
minute(current_date)
second(current_date)
 
FIREBIRD
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from current_date)
extract(minute from current_date)
extract(second from current_date)
 
H2
extract(year from current_date())
extract(month from current_date())
extract(day from current_date())
extract(hour from current_date())
extract(minute from current_date())
extract(second from current_date())
 
HSQLDB
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from current_date)
extract(minute from current_date)
extract(second from current_date)
 
MARIADB
extract(year from current_date())
extract(month from current_date())
extract(day from current_date())
extract(hour from current_date())
extract(minute from current_date())
extract(second from current_date())
 
MYSQL
extract(year from current_date())
extract(month from current_date())
extract(day from current_date())
extract(hour from current_date())
extract(minute from current_date())
extract(second from current_date())
 
POSTGRES
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from current_date)
extract(minute from current_date)
extract(second from current_date)
 
SQLITE
strftime('%Y', current_date)
strftime('%m', current_date)
strftime('%d', current_date)
strftime('%H', current_date)
strftime('%M', current_date)
strftime('%S', current_date)

Коммерческие базы данных

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ACCESS
datepart('yyyy', date())
datepart('m', date())
datepart('d', date())
datepart('h', date())
datepart('n', date())
datepart('s', date())
 
ASE
datepart(yy, current_date())
datepart(mm, current_date())
datepart(dd, current_date())
datepart(hh, current_date())
datepart(mi, current_date())
datepart(ss, current_date())
 
DB2
year(current_date)
month(current_date)
day(current_date)
hour(current_date)
minute(current_date)
second(current_date)
 
HANA
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from current_date)
extract(minute from current_date)
extract(second from current_date)
 
INFORMIX
year(current year to day)
month(current year to day)
day(current year to day)
current year to day::datetime hour to hour::char(2)::int
current year to day::datetime minute to minute::char(2)::int
current year to day::datetime second to second::char(2)::int
 
INGRES
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from current_date)
extract(minute from current_date)
extract(second from current_date)
 
ORACLE (in jOOQ 3.5)
to_char(trunc(sysdate), 'YYYY')
to_char(trunc(sysdate), 'MM')
to_char(trunc(sysdate), 'DD')
to_char(trunc(sysdate), 'HH24')
to_char(trunc(sysdate), 'MI')
to_char(trunc(sysdate), 'SS')
 
ORACLE (in jOOQ 3.6)
extract(year from current_date)
extract(month from current_date)
extract(day from current_date)
extract(hour from cast(current_date as timestamp))
extract(minute from cast(current_date as timestamp))
extract(second from cast(current_date as timestamp))
 
SQLSERVER
datepart(yy, convert(date, current_timestamp))
datepart(mm, convert(date, current_timestamp))
datepart(dd, convert(date, current_timestamp))
datepart(hh, convert(date, current_timestamp))
datepart(mi, convert(date, current_timestamp))
datepart(ss, convert(date, current_timestamp))
 
SYBASE
datepart(yy, current date)
datepart(mm, current date)
datepart(dd, current date)
datepart(hh, current date)
datepart(mi, current date)
datepart(ss, current date)

Да. Стандарт … Если бы он был полностью реализован …

Ссылка: Как извлечь часть даты в SQL от нашего партнера по JCG Лукаса Эдера из блога JAVA, SQL и JOOQ .
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