在SQL中什么时候应该使用函数而不是存储过程,反之亦然?每一个的目的是什么?
当前回答
STORE PROCEDURE | FUNCTION (USER DEFINED FUNCTION) |
---|---|
Procedure can return 0, single or multiple values | Function can return only single value |
Procedure can have input, output parameters | Function can have only input parameters |
Procedure cannot be called from a function | Functions can be called from procedure |
Procedure allows select as well as DML statement in it | Function allows only select statement in it |
Exception can be handled by try-catch block in a procedure | Try-catch block cannot be used in a function |
We can go for transaction management in procedure | We can not go for transaction management in function |
Procedure cannot be utilized in a select statement | Function can be embedded in a select statement |
Procedure can affect the state of database means it can perform CRUD operation on database | Function can not affect the state of database means it can not perform CRUD operation on database |
Procedure can use temporary tables | Function can not use temporary tables |
Procedure can alter the server environment parameters | Function can not alter the environment parameters |
Procedure can use when we want instead is to group a possibly- complex set of SQL statements | Function can use when we want to compute and return a value for use in other SQL statements |
其他回答
用户定义函数是sql server程序员可用的重要工具。您可以像这样在SQL语句中内联使用它
SELECT a, lookupValue(b), c FROM customers
其中lookupValue将是UDF。这种功能在使用存储过程时是不可能实现的。同时,您不能在UDF中做某些事情。这里要记住的基本事情是UDF的:
不能产生永久的变化 无法更改数据
存储过程可以做这些事情。
对我来说,UDF的内联使用是UDF最重要的使用。
下面是一个总结差异的表格:
Stored Procedure | Function | |
---|---|---|
Returns | Zero or more values | A single value (which may be a scalar or a table) |
Can use transaction? | Yes | No |
Can output to parameters? | Yes | No |
Can call each other? | Can call a function | Cannot call a stored procedure |
Usable in SELECT, WHERE and HAVING statements? | No | Yes |
Supports exception handling (via try/catch)? | Yes | No |
STORE PROCEDURE | FUNCTION (USER DEFINED FUNCTION) |
---|---|
Procedure can return 0, single or multiple values | Function can return only single value |
Procedure can have input, output parameters | Function can have only input parameters |
Procedure cannot be called from a function | Functions can be called from procedure |
Procedure allows select as well as DML statement in it | Function allows only select statement in it |
Exception can be handled by try-catch block in a procedure | Try-catch block cannot be used in a function |
We can go for transaction management in procedure | We can not go for transaction management in function |
Procedure cannot be utilized in a select statement | Function can be embedded in a select statement |
Procedure can affect the state of database means it can perform CRUD operation on database | Function can not affect the state of database means it can not perform CRUD operation on database |
Procedure can use temporary tables | Function can not use temporary tables |
Procedure can alter the server environment parameters | Function can not alter the environment parameters |
Procedure can use when we want instead is to group a possibly- complex set of SQL statements | Function can use when we want to compute and return a value for use in other SQL statements |
这里有一个更喜欢函数而不是存储过程的实际原因。如果有一个存储过程需要另一个存储过程的结果,则必须使用insert-exec语句。这意味着您必须创建一个临时表并使用exec语句将存储过程的结果插入到临时表中。它是混乱的。这样做的一个问题是insert-execs不能嵌套。
如果您使用调用其他存储过程的存储过程,可能会遇到这种情况。如果嵌套存储过程只是返回一个数据集,则可以将其替换为表值函数,这样就不会再出现此错误。
(这是我们应该将业务逻辑排除在数据库之外的另一个原因)
SQL Server函数,比如游标,是你最后的武器!它们确实存在性能问题,因此应该尽可能避免使用表值函数。谈论性能就是谈论一个有超过1,000,000条记录的表托管在一个中产阶级硬件的服务器上;否则,您不需要担心函数对性能的影响。
永远不要使用函数将结果集返回给外部代码(如ADO.Net) 尽可能使用视图/存储procs组合。您可以使用DTA(数据库调优顾问)给您的建议(比如索引视图和统计数据)来解决未来的增长性能问题——有时!
如需进一步参考,请参阅:http://databases.aspfaq.com/database/should-i-use-a-view-a-stored-procedure-or-a-user-defined-function.html
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