MySql与SqlServer的一些常用用法的差别
本文将主要列出MySql与SqlServer不同的地方，且以常用的存储过程的相关内容为主。
1. 标识符限定符
SqlServer []
MySql “
2. 字符串相加
SqlServer 直接用 +
MySql concat()
3. isnull()
SqlServer isnull()
MySql ifnull()
注意：MySql也有isnull()函数，但意义不一样
4. getdate()
SqlServer getdate()
MySql now()
5. newid()
SqlServer newid()
MySql uuid()
6. @@ROWCOUNT
SqlServer @@ROWCOUNT
MySql row_count()
注意：MySql的这个函数仅对于update, insert, delete有效
7. SCOPE_IDENTITY()
SqlServer SCOPE_IDENTITY()
MySql last_insert_id()
8. if … else …
SqlServer IF Boolean_expression
{ sql_statement | statement_block }
[ ELSE
{ sql_statement | statement_block } ]
— 若要定义语句块，请使用控制流关键字 BEGIN 和 END。
MySql IF search_condition THEN statement_list
[ELSEIF search_condition THEN statement_list] …
[ELSE statement_list]
END IF
注意：对于MySql来说，then, end if是必须的。类似的还有其它的流程控制语句，这里就不一一列出。
9. declare
其实，SqlServer和MySql都有这个语句，用于定义变量，但差别在于：在MySql中，DECLARE仅被用在BEGIN … END复合语句里，并且必须在复合语句的开头，在任何其它语句之前。这个要求在写游标时，会感觉很BT.
10. 游标的写法
SqlServer declare @tempShoppingCart table (ProductId int, Quantity int)
insert into @tempShoppingCart (ProductId, Quantity)
select ProductId, Quantity from ShoppingCart where UserGuid = @UserGuid
declare @productId int
declare @quantity int
declare tempCartCursor cursor for
select ProductId, Quantity from @tempShoppingCart
open tempCartCursor
fetch next from tempCartCursor into @productId, @quantity
while @@FETCH_STATUS = 0
begin
update Product set SellCount = SellCount + @quantity where productId = @productId
fetch next from tempCartCursor into @productId, @quantity
end
close tempCartCursor
deallocate tempCartCursor
MySql declare m_done int default 0;
declare m_sectionId int;
declare m_newsId int;
declare _cursor_SN cursor for select sectionid, newsid from _temp_SN;
declare continue handler for not found set m_done = 1;
create temporary table _temp_SN select sectionid, newsid from SectionNews group by sectionid, newsid having count(*) > 1;
open _cursor_SN;
while( m_done = 0 ) do
fetch _cursor_SN into m_sectionId, m_newsId;
if( m_done = 0 ) then
— 具体的处理逻辑
end if;
end while;
close _cursor_SN;
drop table _temp_SN;
注意：为了提高性能，通常在表变量上打开游标，不要直接在数据表上打开游标。
11. 分页的处理
SqlServer create procedure GetProductByCategoryId(
@CategoryID int,
@PageIndex int = 0,
@PageSize int = 20,
@TotalRecords int output
)
as
begin
declare @ResultTable table
(
RowIndex int,
ProductID int,
ProductName nvarchar(50),
CategoryID int,
Unit nvarchar(10),
UnitPrice money,
Quantity int
);
insert into @ResultTable
select row_number() over (order by ProductID asc) as RowIndex,
p.ProductID, p.ProductName, p.CategoryID, p.Unit, p.UnitPrice, p.Quantity
from Products as p
where CategoryID = @CategoryID;
select @TotalRecords = count(*) from @ResultTable;
select *
from &n
