T-SQL和MySQL的⼀些常⽤语法的区别本⽂将主要列出MySql与SqlServer的SQL语句的⼀些常⽤语法的不同之处，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 ...isnull的用法
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
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;
MySql 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
以上只是列出了本⼈认为经常在写存储过程中会遇到的⼀些具体的差别之处。

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