pgsql获取上一个月，上一个月第一天，上一个月最后一天

测试数据：

 select 
TO_CHAR((DATE_TRUNC('MONTH', CURRENT_DATE) + INTERVAL '-1 MONTH')::DATE,'YYYYMM') AS "LAST_MONTH",
TO_CHAR((DATE_TRUNC('MONTH', CURRENT_DATE) + INTERVAL '-1 MONTH')::DATE,'YYYYMMDD') AS "LASST_MONTH_FIRST_DAY",
TO_CHAR((DATE_TRUNC('MONTH', CURRENT_DATE) + INTERVAL '-1 DAY')::DATE,'YYYYMMDD') AS "LASST_MONTH_END_DAY"

 

select 
TO_CHAR((DATE_TRUNC('MONTH',TO_DATE('20220521','YYYYMMDD')) + INTERVAL '-1 MONTH')::DATE,'YYYYMM') AS "LAST_MONTH",
TO_CHAR((DATE_TRUNC('MONTH',TO_DATE('20220521','YYYYMMDD')) + INTERVAL '-1 MONTH')::DATE,'YYYYMMDD') AS "LASST_MONTH_FIRST_DAY",
TO_CHAR((DATE_TRUNC('MONTH',TO_DATE('20220521','YYYYMMDD')) + INTERVAL '-1 DAY')::DATE,'YYYYMMDD') AS "LASST_MONTH_END_DAY"