EXEC用法总结

一、使用EXEC执行存储过程

例如存储过名为：myprocedure

use AdventureWorks

create procedure myprocedure @city varchar(20)

as

begin

    select * from Person.Address

end

exec myprocedure @city = 'Bothell'

--或

exec myprocedure 'Bothell'

二、使用EXEC执行动态的SQL语句

注意：动态的sql必须包含于圆括号内如：

exec ('select * from mytable')

使用EXEC执行动态sql语句注意下面问题

1.不能有输入参数，输出参数

下面的脚本是错误的：

DECLARE @i AS INT;
SET @i = 10248;

DECLARE @sql AS VARCHAR(52);
SET @sql = 'SELECT * FROM dbo.Orders WHERE OrderID = @i;';
EXEC(@sql);
GO

2.园括号内部能使用函数或case表达式

下面的脚本是错误的：

DECLARE @schemaname AS NVARCHAR(128), @tablename AS NVARCHAR(128);
SET @schemaname = N'dbo';
SET @tablename = N'Order Details';
EXEC(N'SELECT COUNT(*) FROM '
     + QUOTENAME(@schemaname) + N'.' + QUOTENAME(@tablename) + N';');
GO

不过把函数放在变量中是可以的：

DECLARE
  @schemaname AS NVARCHAR(128),
  @tablename AS NVARCHAR(128),
  @sql AS NVARCHAR(539);
SET @schemaname = N'dbo';
SET @tablename = N'Order Details';
SET @sql = N'SELECT COUNT(*) FROM '
  + QUOTENAME(@schemaname) + N'.' + QUOTENAME(@tablename) + N';'
EXEC(@sql);

3.不能利用重用执行计划，存所以存在性能问题

DECLARE @i AS INT;
SET @i = 10248;

DECLARE @sql AS VARCHAR(52);
SET @sql = 'SELECT * FROM dbo.Orders WHERE OrderID = '
  + CAST(@i AS VARCHAR(10)) + N';';
EXEC(@sql);
GO

当@i = 10248, 10249, 10250要生成3个执行计划。

4。容易被sql注入，存在安全问题。

DECLARE @lastname AS NVARCHAR(40), @sql AS NVARCHAR(200);
SET @lastname = N''' DROP TABLE dbo.Employees --';
SET @sql = N'SELECT * FROM dbo.Employees WHERE LastName = '''
  + @lastname + ''';';
EXEC @sql;
GO

实际执行的sql为：

SELECT * FROM dbo.Employees WHERE LastName = '' DROP TABLE dbo.Employees --';