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 @ResultTable
where RowIndex > (@PageSize * @PageIndex) and RowIndex <= (@PageSize * (@PageIndex+1));
end;
当然，SqlServer中并不只有这一种写法，只是这种写法是比较常见而已。 |
| MySql |
create procedure GetProductsByCategoryId(
in _categoryId int,
in _pageIndex int,
in _pageSize int,
out _totalRecCount int
)
begin
set @categoryId = _categoryId;
set @startRow = _pageIndex * _pageSize;
set @pageSize = _pageSize;
prepare PageSql from
'select sql_calc_found_rows * from product where categoryId = ? order by ProductId desc limit ?, ?';
execute PageSql using @categoryId, @startRow, @pageSize;
deallocate prepare PageSql;
set _totalRecCount = found_rows();
end
|
