Basic knowledge of SQL conversion functions (SQL Server)

1. Cast

Cast (columnname as nvarchar (30) columnname is converted to bytes

2. Round

Round (columnname, 2) takes two decimal places

3. Convert

Select convert (varchar (12), getdate (), 102) -- 2012.12.26
Select convert (varchar (12), getdate (), 111) -- 2012/12/26
Select convert (varchar (12), getdate (), 112) -- 20121226
Select convert (varchar (23), getdate (), 121) -- 23:21:56. 910
Select convert (varchar (19), getdate (), 120) -- 23:21:56
Select convert (varchar (10), getdate (), 120) --
Select convert (varchar (8), getdate (), 114) -- 23:21:56

4. getdate ()

Select getdate () -- 2012-12-26 23:21:56. 910

5. datepart

Select datepart (year, getdate () --- 2012
Select datepart (quarter, getdate () -- 4
Select datepart (month, getdate () -- 12
Select datepart (day, getdate () -- 26
Select Day (getdate () -- 26
Select datepart (dy, getdate () -- 361 [add dy to day of year, the day of the year]
Select datepart (weekday, getdate () -- 4 [minus 1, because foreign countries are different from China, indicating Today's Wednesday]
Select datepart (Week, getdate () -- 52 [week 52nd]
Select datepart (hour, getdate () -- 23
Select datepart (minute, getdate () -- 21
Select datepart (second, getdate () -- 56
Select datepart (millisecond, getdate () -- 910

6. datename

Select datename (day, getdate () -- 26
Select datename (dy, getdate () -- 361
Select datename (weekday, getdate () -- Wednesday [note the difference with datepart]
Select datename (Week, getdate () -- 52

7. dateadd, time Addition

Select dateadd (day, 3, getdate () -- 23:21:56. 910
Select dateadd (month, 3, getdate () -- 23:21:56. 910

8. datediff, time subtraction, followed by time minus the previous time difference

Select datediff (day, '2017-12-20 ', getdate () -- 6
Select datediff (month, '2014-12-20 ', getdate () -- 0

9. Rand

Select cast (floor (RAND (checksum (newid () * 100) as INT)