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 |