本文將主要列出MySql與SqlServer不同的地方,且以 常用的 存儲過程的相關內容為主。
1. 標識符限定符
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()函數,但意義不一樣 |
4. getdate()
SqlServer | getdate() |
MySql | now() |
5. newid()
SqlServer | newid() |
MySql | uuid() |
6. @@ROWCOUNT
SqlServer | @@ROWCOUNT |
MySql |
row_count()
注意:MySql的這個函數僅對于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 } ] -- 若要定義語句塊,請使用控制流關鍵字 BEGIN 和 END。 |
MySql |
IF search_condition THEN statement_list [ELSEIF search_condition THEN statement_list] ... [ELSE statement_list] END IF |
注意:對于MySql來說,then, end if是必須的。類似的還有其它的流程控制語句,這里就不一一列出。
9. declare
其實,SqlServer和MySql都有這個語句,用于定義變量,但差別在于:在MySql中,DECLARE僅被用在BEGIN ... END復合語句里,并且必須在復合語句的開頭,在任何其它語句之前。這個要求在寫游標時,會感覺很BT.
10. 游標的寫法
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 -- 具體的處理邏輯 end if; end while; close _cursor_SN; drop table _temp_SN; |
注意:為了提高性能,通常在表變量上打開游標,不要直接在數據表上打開游標。
11. 分頁的處理
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; 當然,SqlServer中并不只有這一種寫法,只是這種寫法是比較常見而已。 |
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 |
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