Archive Name And Parameters Vs Perimeters
Project Parameters are certain characteristics and features that can define a project or its aspects home. Articles Archive. What are Project Parameters. Archive Name And Parameters Vs Perimeters. 3/10/2017 0 Comments Calculating the area and the perimeter. Give the parameter a logical name. Revit Parameters Part 1. Archive Name And Parameters Vs Statistics. 5/30/2017 0 Comments Using SQL Server's Table Valued Parameters. Table valued parameters. August 2017 July 2017.
Project Parameters are certain characteristics and features that can define a project or its aspects. These parameters (project characteristics) can be expressed in different ways, including qualitative and quantitative terms – strict figures, technical wording, graphs, statusing, etc.
Problem One of the benefits of SQL is the ability to write a query and use parameters to dynamically act upon the resultset. Depending on the situation, there can be benefits to parameterizing queries, but it is not always clear when or how to do this. In this tip we look at different ways to pass in values as parameters to queries and the advantages and disadvantages. Solution Properly parameterizing queries can bring advantages such as:. Encouraging for complex queries. Providing some protection against SQL Injection Attacks under some circumstances Generally, when creating a condition in a query where you might use one of several values, it makes sense to parameterize.
But, as will be discussed later in this tip, there are cases where the query cannot be fully parameterized. Parameterizing a Query By Making It a Stored Procedure If you want to find the sales data for Jack, you could start with a non-parameterized query that just pulls up that data. Create procedure getSalespersonbad @sp varchar(25) as declare @sql varchar(max) set @sql = ' select SalesPerson, Mon, amount from SalesData where SalesPerson = ' + @sp + ';' exec (@sql) Go This second version builds a non-parameterized query using dynamic sql. It is simple to exploit a procedure like this in a SQL Injection Attack. It also does not explicitly tell SQL Server where the parameters are.
Parameterizing in T-SQL with spexecutesql Another direct way to parameterize a query in T-SQL is to use and explicitly add your parameters. It looks like. Declare @sql nvarchar(4000) declare @monthNo int declare @minAmount decimal set @sql = N' select SalesPerson from dbo.SalesData where mon = @MonthNo and amount @minAmount' set @monthNo = 2 set @minAmount = 100 exec spexecutesql @sql, N'@monthNo int, @minAmount decimal', @monthNo, @minAmount With spexecutesql the first parameter is the SQL code to be executed, the second lists the parameters that will be supplied and indicates whether they are output variables, and then the actual parameters are passed into the procedure. Both the SQL statement and the list of parameters must be presented in unicode (nvarchar, nchar, or a string prefixed by N like the parameter list in the example.) Parameterizing in SQL from other languages Languages that interact with SQL tend to make it simple to parameterize. To parameterize a put the names of the parameters in the CommandText and then use to add parameters that match the name to the command before executing.
It looks like. Import pyodbc connString = (r'YourConnString') conn = pyodbc.connect(connString) curs = conn.cursor sql = 'select SalesPerson from dbo.SalesData where mon =?
And amount ?' ' curs.execute(sql, (2, 100.00)) for result in curs: print result When the query cannot be (fully) parameterized Parameterization brings several benefits, including some protection against SQL injection attacks under some circumstances.
But there are certain types of dynamic queries that cannot be fully parameterized. For instance, SQL Server will not accept a table name or a column name as a parameter. If you tried to do it with spexecutesql, like. Declare @sql nvarchar(4000) declare @colName nvarchar(256) set @sql = N' select @colName from dbo.SalesData where mon = 2 and amount 100.0' set @colName = 'SalesPerson' exec spexecutesql @sql, N'@colName nvarchar(256)', @colName The server merely returns a result set of 'SalesPerson'. Trying to use a parameter for a tablename in a query causes the server to try to interpret the parameter as a table variable and gives an error like: 'Msg 1087, Level 16, State 1, Line 3 Must declare the table variable '@tableName'.'
So a procedure meant to run against an would need to actually build the SQL command by constructing the string. Other parts of that query could still be parameterized of course. A simplified example could look like.
Set @tableName = 'SalesData' set @monthNo = 2 set @sql = N' select SalesPerson from ' + @tableName + ' where mon = @monthNo' exec spexecutesql @sql, N'@monthNo int', @monthNo However, building the string that way can make SQL Injection attacks simpler, especially if the user is directly prompted to supply the table or column names. Depending on the expected use cases, it may be wise to perform some string validation before execution. Ensuring the application runs with the to SQL Server can help mitigate that risk to a degree. Summary In general, properly applied parameterization can assist in security for SQL Server and can have.
But, some queries cannot be fully parameterized such as when the column names, table names, or other clauses need to be added or modified dynamically. When non-parameterized dynamic SQL is used, the performance and security implications should be kept in mind. Next Steps. To find more on parameterizing in the context of dynamic SQL, look at Erland Sommarskog's. has more on using parameterization as one layer of defense against some SQL injection attacks. Essentials of investments zvi bodie pdf writer. has more on execution plan reuse.
has more information on how to encourage SQL Server to reuse query execution plans without explicitly parameterizing the queries yourself. Last Update: 2013-06-19. Post a comment or let the author know this tip helped. All comments are reviewed, so stay on subject or we may delete your comment.
Note: your email address is not published. Required fields are marked with an asterisk (.).Name.Email Notify for updates. NOTE. If you want to include code from SQL Server Management Studio (SSMS) in your post, please copy the code from SSMS and paste the code into a text editor like NotePad before copying the code below to remove the SSMS formatting.
Send me SQL tips. Thursday, September 21, 2017 - 11:16:35 PM - Evgenii Thank you! Sunday, January 01, 2017 - 1:51:24 AM - AbdurrhmanZaki Thanks alot, it helped me. Friday, January 30, 2015 - 1:27:07 AM - jaineesh I have one doubt in table 'RAJ' is a employee. His experience is 5 years, i need the below experience of 'RAJ' any body send the query Tuesday, February 04, 2014 - 12:43:48 PM - Scott Coleman If you use SQLCMD mode in Management Studio, you can parameterize your scripts with:SETVAR. The parameter values are added by simple text replacement before the query is sent to the server, so they can be used anywhere. Table names, database names, server names, string literals, or pieces of any of those.
Archive Name And Parameters
The script can be multiple batches separated by GO, and the SQLCMD variables are applied to the whole thing.:SETVAR SERVER myServer:SETVAR DB myDatabase:SETVAR SCHEMA mySchema:SETVAR TABLEROOT myTable:SETVAR TABLESUFFIX dev:SETVAR KEY PKcolumn:SETVAR FILTER 'LIKE 'xyz%' SELECT 'Server=$(SERVER)', 'Database=$(DB)',. FROM $(SERVER).$(DB).$(SCHEMA).$(TABLEROOT)$(TABLESUFFIX) WHERE $(KEY) $(FILTER) Wednesday, June 19, 2013 - 7:12:30 PM - TimothyAWiseman Wilfred, thank you for the feedback. Parameter sniffing is expected behavior and is normally desirable.
To perhaps oversimplify, if a query is called that is not in the cache, SQL server must compile it. When it does so, it will look at or 'sniff' the parameters used for that query and optimize its execution plan for those values. The 'Parameter Sniffing Problem' arises if there is a plan in the cache, but the plan was suboptimal this time because it was optimized for parameters that would return a different cardinality. For instance, a query that would only return a few values might be best with a very different execution plan than one that would return 90% of the values in the table. Although this problem can arise for just about any query, it is most common in queries that involve the use of 'LIKE' and wildcards like '%'.
Although this can be a performance problem in some situations, this problem is often well outweighed by the benefits of execution plan reuse, elegance of code, and (in some situations) security benefits that come from proper parameterization. It is also worth noting that using dynamic SQL or not parameterizing your code will not always prevent the 'parameter sniffing problem' because later versions of SQL Server will sometimes parameterize simple queries behindt he scenes in order to gain the benefits of query plan reuse. The excellent tip ' by Brady Upton mentions this.
Perimeters Vs Parameters
Now, if parameter sniffing does cause performance problems in your particular case there are a number of ways to address it. One way is to include such as as Greg Robidoux talked about in his tip.
Difference Between Perimeter And Parameter
Greg Larson also has an detailing how this problem can come up, why it often does not come up, and options on how to deal with it when it does come up that might be useful. Wednesday, June 19, 2013 - 9:38:09 AM - Jeremy Kadlec Wilfred, Thank you for the post. Here are some additional tips to consider: HTH. Thank you, Jeremy Kadlec Community Co-Leader Wednesday, June 19, 2013 - 9:23:39 AM - Wilfred van Dijk Before everybody starts to rewrite their code, make sure you´re also known with a big issue with parameters called the ´Parameter sniffing´ problem.