AS @recursive: you can't have indexes on a table variable, which will often make it slower than a subquery. GUID in Sql Server August 17, 2020; PIVOT, Multi Pivot & Dynamic Pivot in SQL Server May 10, 2020; Mutex in Sql Server November 27, 2019; Recursive CTE October 15, 2019; Bookmark lookup tipping point September 16, 2019; RECENT COMMENTS. IF EXISTS ( SELECT * FROM dbo.AccountDetails WHERE Email = @Email ) In particular, pay very close attention to your average use case. It doesn't apply to one-off analysis scripts - unless I'm the author.). The only intent of this post is to introduce a number of the anti-patterns I see in the field which you may want to avoid (or at least limit). Why did DEC develop Alpha instead of continuing with MIPS? As it currently stands, this question is not a good fit for our Q&A format. Comment by JFO — October 26, 2018 @ 7:10 am, Yes, you’re right that’s a subtle distinction. This query requires two or three different execution plans depending on the values of the parameters. Re-using a 'dead' field for something it wasn't intended for (e.g. I wanted to bring all those ideas together on one page. Luckily, it's often easy to test, and different options work with different db needs. They are not even different things that are optimized to one another, but just different textual representations of the same operation. (more thoughts on it... http://writeonly.wordpress.com/2008/12/05/simple-object-db-using-json-and-python-sqlite/). My favorite is when people embed HTML AND javascript, e.g. This might not seem like it’s too bad — they’re just integers, and we have plenty of those, right? @JackRyan: This is bad because when you change the enum list later, you need to remember to change it in two places now. Serializable isolation is sort of an anti-pattern, since it hampers concurrent writes to the table being upserted to. But now I think that retries are a necessary part of the transaction landscape and they becomes almost necessary when considering more distributed solutions, or other high-availability solutions in general. -- This statement will not insert if there's already a duplicate row. Anti Patterns are common in Sql, where programmers used to procedural languages build models that would work well in a procedural environment, but in the Sql environment result in very large numbers of queries or avoidable replication of data. Comment by tobi — September 12, 2017 @ 1:58 pm. Only one execution plan is generated and stuck into the cache for this SQL text. True it can be abused to extremes. Such anti-patterns often slow down queries. Best practice: Avoid self-joins. What are the common antipatterns you've seen (or yourself committed)? I had to protest really loud. Number 2. CREATE PROCEDURE s_AccountDetails_Upsert ( @Email nvarchar(4000), @Etc nvarchar(max) ) just say LIKE in general. To mitigate do not share views with other projects and, use CTEs when platforms allow. @doofledorfer: Agree, a middle tier would be definitely better in a case like this, plus providing results caching as a nice side effect. Learning SQL in the first six months of their career and never learning anything else for the next 10 years. end Id rather have an enum in my app code that maps to an enum constraint in my DB than an enum in my app code that maps to specific rows of a lookup table. Developers who write queries without having a good idea about what makes SQL applications (both individual queries and multi-user systems) fast or slow. I'll describe those together with suggestions of solving them. This question is a perfect example of all that is wrong with StackExchange. Why this is an anti-pattern: Prior to SQL Server 2012 SP1, tables statistics not available for foreign servers unless linked server account is sysadmin, db_owner, or db_ddladmin. In particular the use of over() and partition by. INSERT (Email, Etc) On most database servers (at least the ones I've used), LIKE can use indexes.. as long as it's a prefix-search (LIKE 'xxx%') -- that is, as long as the wildcard characters don't come first in the search string. SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; We focus on design errors (antipatterns), which typically lead to unnecessary SQL statements. SQL Server 2019 Express is a free edition of SQL Server, ideal for development and production for desktop, web, and small server applications. All of which can usefully be dealt with by using a database abstracton layer of some (any) kind. In other words, antipatterns share the characteristics of being: * Common, i.e. If it's a stored procedure, put the test statement into a comment and save it, with the results. For development updates on sqlcheck and general news on next generation database systems, follow me at @joy_arulraj. Overuse of anything is by definition unwanted. Used a previous comment's query, just because that was the first SQL-statement I had available. Could you please share the .sqlstress file? Comment by Michael J. Swart — October 6, 2017 @ 9:27 am. VALUES (@Email, @Etc); Nothing says It may not be good for de-coupling, though for performance reasons I've done stuff like that often, iterative changes done by SQL Server are faster than done by code in mid-tier. else if (xact_state() -1) rollback tran outerTran Comment by Michael J. Swart — July 27, 2017 @ 9:28 am. will. (Indexes order by the 1st character 1st, and so looking at the middle 4 characters gives a virtually random order...). I have to admit that I’ve never thought about using sp_getapplock that way. noSQL solutions are showing a performance benefit at the cost of duplicate data by eliminating multi-table lookups. -- Only open a new transaction if there is no outer transaction, -- (We're going to tie the app lock to our transaction -- which means a rollback or commit will unlock), SQL Server UPSERT Patterns and Antipatterns, Serializable Transactions With Lock Hints, Mythbusting: Concurrent Update/Insert Solutions, Case study: Troubleshooting Doomed Transactions, Checking for potential constraint violations before entering SQL Server TRY and CATCH logic, https://michaeljswart.com/2016/02/future-proofing-for-concurrency/, Sync Sitecore content to external database | Brian Pedersen's Sitecore and .NET Blog, I updated the query in this post to run inside SQL Query stress, the way emails are generated now, there is a better chance of key collisions. Sometimes it is, sometimes it isn't. If your workload UPDATEs a row 99% of the time and INSERTs a row only 1% of the time, then optimal implementation will look different than if the UPDATE and INSERT frequency is reversed. Just try it and catch and swallow any exception, CREATE PROCEDURE s_AccountDetails_Upsert ( @Email nvarchar(4000), @Etc nvarchar(max) ) 2) date/string conversion that relies on specific NLS settings. using @@IDENTITY instead of SCOPE_IDENTITY(). 8 January 2012. Or change the content of an export, or reformat a date in a report. else begin I didn’t mention this, but remember to delete all the rows from AccountDetails when you begin each run. AS Martin, Comment by Martin — July 26, 2017 @ 5:42 am, I think there are a few things I could suggest. What? Load comments. The Altered View - A view that is altered too often and without notice or reason. It is much better to write two queries (one query per intended execution plan). This can be a factor in control-break reports. UPDATE dbo.AccountDetails It's a RAD environment, with a very simple database manager included. or an objects it depends on is modified you'll receive an error just by asking for an execution plan! Disk space is cheap, and sometimes it can be simpler (easier code, faster development time) to manipulate / filter / search fetched data, than it is to write up 1NF schema, and deal with all the hassles therein (complex joins, nasty subselects, etc). The change will either be noticed at the most inappropriate time or worse be wrong and never noticed. Azure SQL DW Anti-Patterns ... Also, SQL Server security features such as Always Encrypted, Row Level Security, Column Level Encryption are not present in Azure SQL DW as of this writing. We have SQL Server at my work, but a number of people use access due to it's availabilty, "ease of use" and "friendliness" to non-technical users. SET etc = mySource.etc Even though it’s a single statement, it’s not isolated enough. If you have a where clause you should have parameters. -- (We're going to tie the app lock to our transaction -- which means a rollback or commit will unlock) Upsert anti-pattern in SQL Server (sqlperformance.com) 95 points by hobs 82 days ago | hide ... this has nothing to do with SQL Server. I would use emp for employee, dep for department and job for job (or maybe jb) :). My favorite antipattern is not testing your queries. Does cyberpunk exclude interstellar space travel? I just put this one together, based on some of the SQL responses here on SO. VALUES ( @Email, @Etc ); Comment by Vladimir Sotirov — September 14, 2020 @ 7:34 pm. However, it's important to have a way to know the timezone of every stored datetime. And for MS SQL server the use of But if all you know is SQL, you either use it inappropriately, or you learn to write other kinds of software. Comment by Michael J. Swart — September 12, 2017 @ 2:28 pm. COMMIT. These are all still antipatterns, because. CREATE PROCEDURE s_AccountDetails_Upsert ( @Email nvarchar(4000), @Etc nvarchar(max) ) CREATE PROCEDURE s_AccountDetails_Upsert ( @Email nvarchar(4000), @Etc nvarchar(max) ) Using primary keys as a surrogate for record addresses and using foreign keys as a surrogate for pointers embedded in records. And the style is rampant in a lot of SQL programs - regardless of programming language. Can a program be an anti-pattern? Good luck Martin, let me know what works for you, I’ll update the post. Many database systems can run code. And I do usually try it both ways. Your experience with sp_getapplock and mine are really really different. UPDATE dbo.AccountDetails WHERE Email = @Email; However, overusing these features can hurt performance, for several reasons: 1. I mean, it will fail under any concurrency load, even if low, just rarer. rev 2020.12.8.38145. That's why I always test it both ways. This is a solid solution, but every implementation is different so every time you use this pattern, test for concurrency. He is the author of a series of SQL Server Database Design books, most recently Pro SQL Server Relational Database Design and Implementation. Today, many scientific data sets are open to the public. If you try putting the vanilla solution inside a transaction, it makes the whole thing atomic, but still not isolated. Cool, have been working with SQL for years, and didn't even know Common Table Expressions exist (though I would have needed them). There is too much here to go into, but if you've been in a similar environment, you know. UPDATE dbo.AccountDetails So when your object gets modified and receives more parameters, or of different type, etc. It violates. Sql server is going to take out a range lock on the key field. Views have a purpose, but when each table is wrapped in a view it's too much. Awesome example. I've seen this a lot, I find this idiotic and does indeed make searching for a particular SP, The prefixes can be useful if you're scripting the objects to files (eg: for source control, deployments or migration), Why on earth would it be useful to prefix every single stored procedure with sp. Despite growing maturity the framework still suffers from problems that often stem from naive implementations. VALUES ( @Email, @Etc ); well...Oracle still won't let you use ANSI joins for, A very useful technique for minimal T-SQL test: In the .SQL file where you define your SP, UDF, etc., immediately after it create a block test like IF 1=2 BEGIN (sample cases for your code, with expected results as comments) END. Tend to use an ORM with SQL Server to Oracle have a way to do that if rule! These common database errors once and for all sql server anti patterns flags, large and... ), which affects reads only way to stop using SQL Server does parse the with. 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