题目情况

数据库版本情况

postgres=# select version();
                                                 version                                                 
---------------------------------------------------------------------------------------------------------
 PostgreSQL 12.9 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
(1 row)

postgres=# 

数据库操作

ostgres=# select now() + interval'2 days';
           ?column?            
-------------------------------
 2022-12-29 11:30:45.691244+08
(1 row)

postgres=# select now()+2;
2022-12-27 11:30:54.595 CST [1798] ERROR:  operator does not exist: timestamp with time zone + integer at character 13
2022-12-27 11:30:54.595 CST [1798] HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
2022-12-27 11:30:54.595 CST [1798] STATEMENT:  select now()+2;
ERROR:  operator does not exist: timestamp with time zone + integer
LINE 1: select now()+2;
                    ^
HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
postgres=# 
postgres=# select current_date+interval'2 days';
      ?column?       
---------------------
 2022-12-29 00:00:00
(1 row)

postgres=# select current_date+2;
  ?column?  
------------
 2022-12-29
(1 row)

postgres=# 

疑问，第二个选项

postgres=# select now() + 2;
2022-12-27 11:36:49.449 CST [1798] ERROR:  operator does not exist: timestamp with time zone + integer at character 14
2022-12-27 11:36:49.449 CST [1798] HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
2022-12-27 11:36:49.449 CST [1798] STATEMENT:  select now() + 2;
ERROR:  operator does not exist: timestamp with time zone + integer
LINE 1: select now() + 2;
                     ^
HINT:  No operator matches the given name and argument types. You might need to add explicit type casts.
postgres=#