最近用到,在网上查了下资料
注意加粗部分,sp_executesql 的参数必须为UNICODE,即NCHAR,NVARCHAR,NTEXT型,否则报错Basic grammar of dynamic sql statement
1: Exec executes
Select * from tableName
Exec ('select * from tableName')
Exec sp_executesql N'select * from tableName '-please note that N must be added before the string
2: field Name, table name, database name, etc. as variables, you must use dynamic SQL
eg:
declare @fname varchar (20)
set @fname = 'FiledName'
Select @fname from tableName-error, no error will be prompted, but the result is The fixed value FiledName is not required.
Exec ( 'select' + @fname + 'from tableName') - Note single quotation marks before and after the edge spaces plus
of course the string variables may also change
DECLARE @fname VARCHAR (20 is)
SET @fname = 'FiledName' --Set field name
declare @s varchar (1000)
set @s = 'select' + @fname + 'from tableName'
Nvarchar (1000)-Note that here changed to nvarchar (1000)
set @s = 'select' + @fname + 'from tableName'
Exec (@s)-successful
exec sp_executesql @s-this sentence is correct
3. Output Parameters
declare @num int,
@sqls nvarchar (4000)
set @ sqls = 'select count (*) from tableName'
exec (@sqls)-how
to put the execution result of exec into a variable?
declare @num int,
@sqls nvarchar (4000)
set @ sqls = 'select @ a = count (*) from tableName'
exec sp_executesql @ sqls, N '@ a int output', @ num output
select @numIf
it is its own There are parameters in the stored procedure, you can also use sp_executesql directly
CREATE PROCEDURE demo
@test varchar(100)
as
return 1
go
declare @name int
exec @name=demo 'test'
select @name
There can be no functions in the parameters of the stored procedure demo
. If you want to pass a newid (), you must use local variables.Note
that the return value of the stored procedure must be an integer
declare @id
declare @name int
exec @ name = demo @id
select @name
mssql help
Execute Transact-SQL statements or batches that can be reused multiple times or dynamically generated. Transact-SQL statements or batches can contain embedded parameters.
grammar
sp_executesql [@stmt =] stmt
[
{, [@params =] N@#@parameter_name data_type [,...n]@# }
{, [@param1 =] @#value1@# [,...n] }
]
parameter
[ @stmt = ] stmt
Containing Transact-SQL statements or batch of Unicode strings, stmt must be a Unicode constant or variable that can be implicitly converted to ntext . More complex Unicode expressions are not allowed (for example, use the + operator to concatenate two strings). Character constants are not allowed. If you specify a constant, you must use N as the prefix. For example, the Unicode constant N @ # sp_who @ # is valid, but the character constant @ # sp_who @ # is invalid. The size of the string is only limited by the available database server memory.
stmt can contain parameters in the same form as variable names, for example:
N@#SELECT * FROM Employees WHERE EmployeeID = @IDParameter@#
Each parameter contained in stmt must have a corresponding item in the @params parameter definition list and parameter value list.
[@params =] N@#@parameter_name data_type [,...n]@#
A string containing definitions of all parameters embedded in stmt . The string must be a Unicode constant or variable that can be implicitly converted to ntext . Each parameter definition consists of the parameter name and data type. n is a placeholder indicating additional parameter definition. Every parameter specified in stmt must be defined in @params . If the Transact-SQL statement or batch in stmt contains no parameters, @params is not required . The default value of this parameter is NULL.
[@param1 =] @#value1@#
The value of the first parameter defined in the parameter string. The value can be a constant or a variable. The parameter value must be provided for each parameter contained in stmt . If the Transact-SQL statement or batch included in stmt has no parameters, no value is required.
n
Placeholder for the value of additional parameters. These values can only be constants or variables, not more complex expressions, such as functions or expressions generated using operators.
Return code value
0 (success) or 1 (failure)
Result set
Return a result set from all SQL statements that generate SQL strings.
Example (thanks to Zou Jian for providing)
declare @user varchar(1000)
declare @moTable varchar(20)
select @moTable = @#MT_10@#
declare @sql nvarchar(4000) --定义变量,注意类型
set @sql=@#select @user = count(distinct userid) from @#+@moTable --为变量赋值
--执行@sql中的语句
exec sp_executesql @sql
,N@#@user varchar(1000) out@# --表示@sql中的语句包含了一个输出参数
,@user out --和调用存储过程差不多,指定输出参数值
print @user
