SQLを使って指定した年月の月末日(28日or29日or30日or31日)を取得する例を以下に記します。
PostgreSQL 11.5
sakuradb=# select version(); version --------------------------------------------------------------------------------------------------------------------------------- PostgreSQL 11.5 (Raspbian 11.5-1+deb10u1) on arm-unknown-linux-gnueabihf, compiled by gcc (Raspbian 8.3.0-6+rpi1) 8.3.0, 32-bit (1 行)
本日(本月)の月末日、1月から12月までの月末日とうるう年の2月月末日を
取得するSQLおよび実行結果を以下に記します。
本月の月末を取得する場合のSQL構文は以下のようになります。
select date_trunc('month',now()) + '1 month' + '-1 days';
now()で本日を取得し、'month'を指定し月精度で切り捨てたあと、
一か月を加算し一日減算することにより月末日を算出しています。
sakuradb=# select date_trunc('month',now()) + '1 month' + '-1 days'; ?column? ------------------------ 2019-11-30 00:00:00+09 (1 行)
以下、2019年1月から12月までの月末をdate_trunc関数を使って取得するSQLになります。
select date_trunc('month',to_date('2019/01/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/02/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/03/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/04/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/05/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/06/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/07/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/08/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/09/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/10/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/11/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/12/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month;
sakuradb=# select date_trunc('month',to_date('2019/01/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-01-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/02/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-02-28 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/03/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-03-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/04/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-04-30 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/05/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-05-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/06/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-06-30 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/07/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-07-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/08/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-08-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/09/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-09-30 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/10/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-10-31 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/11/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; select date_trunc('month',to_date('2019/12/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-11-30 00:00:00+09 (1 行) sakuradb=# select date_trunc('month',to_date('2019/12/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2019-12-31 00:00:00+09 (1 行)
2020年2月の月末日を取得します。
sakuradb=# select date_trunc('month',to_date('2020/02/01','YYYY/MM/DD')) + '1 month' + '-1 days' as end_of_month; end_of_month ------------------------ 2020-02-29 00:00:00+09 (1 行)
以上、PostgreSQLのdate_trunc関数を使って指定した月の月末日を取得する方法でした。