Oracle Database SQL operations

SQL statement for time field query:

Select * From mycontent t where T. create_date <= to_date ('2017-06-21 ', 'yyyy-mm-dd ')

SQL statement for modifying the time field:

Update mycontent t
Set T. create_date = to_date ('2017. 2012 13:10:45 ',
'Yyyy-mm-dd hh24: MI: ss '),
T. modify_date = to_date ('2017. 2012 13:10:45 ',
'Yyyy-mm-dd hh24: MI: ss ')
Where T. content_id = '20140901'

Statement for querying the lock table:

Select sess. Sid,
Sess. Serial #,
Lo. oracle_username,
Lo. OS _user_name,
AO. object_name,
Lo. locked_mode
From v $ locked_object Lo, dba_objects AO, V $ session sess
Where ao. object_id = Lo. object_id
And lo. session_id = sess. Sid;

Query Result string addition:

Select * 'HTTP: // www.baidu.com/index.jsp? Contentid = '| T. content_id as mylink
From mycontent t

Recursive query display:

Select Replace (replace (category_code,
'1 ',
'0 '),
'2 ',
'0 '),
'3 ',
'0 '),
'4 ',
'0 '),
'5 ',
'0 '),
'6 ',
'0 '),
'7 ',
'0 '),
'8 ',
'0 '),
'9 ',
'0') | C. category_name,
C. category_code
From mycategory C
Where C. category_code like '20140901'
Order by C. category_code