[Database] [Sybase] datetime-related example

Here has some examples:

-- get current timestamp
select getdate();

-- cast datetime string to datetime
select cast('2018-07-13 23:59:59' as datetime);

-- get year from datetime
select year(getdate());

-- get month from datatime
select month(getdate());

-- get day from datetime
select day(getdate());

-- get datetime string with YYYY-MM-DD hh:mm:ss format
select str_replace(CONVERT (VARCHAR, getdate(), 23), 'T', ' ') ;

-- add 3 days
select dateadd(day, 3, getdate());

-- minus 10 days
select dateadd(day, -10, getdate());

-- add 2 hours
select dateadd(hh, 2, getdate());

-- minus 3 hours
select dateadd(hh, -3, getdate()) 

-- get current datetime and set its time to 0:0:0
select cast(substring(convert(varchar, getdate(), 23), 1, 10) + ' 0:0:0' as datetime);