SQL Server learning notes

1. cast(lx as nvarchar) sqlserver String concatenation
2. sql server To realize mysql Of find_in_set function

CHARINDEX(cast( {
    } as nvarchar),ancestors) > 0

3. Insert another table after the query result

INSERT INTO [dbo].[sys_role_menu_tmp] SELECT * FROM [dbo].[sys_role_menu];

4. stay SQL Server in , I won't support it Limit sentence , It can be solved in the following ways .
   although SQL Server I won't support it Limit , But it supports TOP.
   （1） If you want to query the top of the above results 6 Bar record , The corresponding SQL The sentence is ：

select top 6 id from tablename

（2） If you want to query the above results 7 To the first article 9 Bar record , The corresponding SQL The sentence is ：

select top 3 id from tablename where id not in (   select top 6 id from tablename )

select top @pageSize id from tablename where id not in (
  select top @offset id from tablename
)

If you want to check n-m Data between The first 4 The number of lines is n-1, The number in the first line is m-n+1, This enables paging .
5. String splicing
MySQL use concat () function ,SQL Server String splicing of adopts “+” complete .
SQL Server：‘a’+‘b’
MySQL：concat (‘a’,‘b’)
6. Get the current time
Mysql：now()
SQL Server：getdate()
7. Date addition and subtraction
Mysql：date_add()
date_add (date,INTERVAL expr type)
Example ：date_add( now(), INTERVAL -1 YEAR)
date_add( now(), INTERVAL 5 DAY)

SQL Server：dateadd()
dateadd (datepart,number,date)
Example ：dateadd (yy, -1, getdate())
dateadd (day, 5, getdate())
8. cast() function
Be careful par Are parameters of conversion

9. Mysql： locate()
   Sql server：charindex()
   

10. character string str Number of characters included
    MySQL： char_length (str)
    SQL Server： len (str) and datalength (str)

11. Transformation format

12. null Judge
    

13. String substitution
    Sql server：stuff()
    Mysql：insert()
    

14. mysql：group_concat() And sql server：for xml path（’’）