SELECT event_time, event_time - INTERVAL '1 day' AS event_time_minus_one_day FROM events; 5. 解释可能遇到的时区或夏令时相关问题及其解决方法 在PostgreSQL中进行时间加减操作时,可能会遇到时区或夏令时相关的问题。为了处理这些问题,你可以使用带有时区的时间戳类型(TIMESTAMP WITH TIME ZONE),并确保你...
CURRENT_DATE(当前日期):SELECT CURRENT_DATE;(返回该函数执行时的时间) SQL Server:SELECT CAST(CURRENT_TIMESTAMP AS DATE) AS CUR_DATE; Oracle:SELECT CURRENT_DATE FROM dual; (dual:临时表) DB2:SELECT CURRENT DATE FROM SYSIBM.SYSDUMMY1; CURRENT_TIME(当前时间):SELECT CURRENT_TIME;(返回函数执行的当...
alter tablespace newsmgm_space add datafile 'D:\Oracle\orsx\oradata\orcl\pdborcl\newsmgm_space_1.dbf' size 10M; 1. 2. 修改表空间的已有的数据文件大小 alter database datafile 'D:\Oracle\orsx\oradata\orcl\pdborcl\newsmgm_space_1.dbf' resize 20M; 1. 设置默认表空间 select property_name,...
Oracle中的sysdate()/sysdate返回系统当前时间(日期+时分秒),在PostgreSQL中对应now()或是current_timestamp(日期+时分秒+毫秒)。 Oracle中的systimestamp返回系统当前时间戳(日期+时分秒+毫秒),在PostgreSQL中对应now()或是current_timestamp。 to_date(str, fmt) Oracle中的to_date返回的是时间类型,而在PostgreSQL...
last_day(date) Oracle中的last_day返回指定日期所在月份的最后一天; 在PostgreSQL没有对应的函数,需将其转化为基于日期和interval的运算。 编号 Oracle PostgreSQL 1 select add_months(sysdate, 2) select cast(date_trunc('MONTH', current_timestamp) + interval '1 MONTH - 1 DAY' as date) SQL语句 HAVIN...
切换数据库(使用uer1登录user1db) postgres=# \c user1db user1 psql (8.4.18, server 10.7) WARNING: psql version 8.4, server version 10.7. Some psql features might not work. You are now connected to database "user1db" as user "user1". ...
{ $$ = NULL; } ; /* variant for UPDATE and DELETE */ where_or_current_clause: WHERE a_expr { $$ = $2; } | WHERE CURRENT_P OF cursor_name { CurrentOfExpr *n = makeNode(CurrentOfExpr); /* cvarno is filled in by parse analysis */ n->cursor_name = $4; n->cursor_param...
And when you add (or subtract) an interval value to (or from) a timestamp[tz] value, you get a timestamp[tz] value. This sounds as if it couldn’t be simpler. But it turns out that the rules here are complex and confusing. I struggled with all this while I was doing the ...
= < <= like between is null in 逻辑运算符:not and or 集合运算符: intersect ,union, union all, minus 要求:对应集合的列数和数据类型相同 查询中不能包含long 列 列的标签是第一个集合的标签 使用order by时,必须使用位置序号,不能使用列名 例:集合运算符的使用: intersect ,union, union all, ...
Converting date and time functions: DB2 PostgreSQL 1 DATE(exp) Convert to date (year, month and day) DATE(exp) Not documented 2 DAY(exp) Extract day EXTRACT(DAY FROM exp) 3 MONTH(exp) Extract month EXTRACT(MONTH FROM exp) 4 TIMESTAMP(exp) Convert to timestamp (date and time)...