All programs only one row

Clear instructions. Easy to follow. No jargon. Pictures helped. Didn't match my screen. Incorrect instructions. Too technical. Not enough information. Not enough pictures. Hello Horst, in the TASK: You want to check the existence of a row There is a performance recommendation by Hermann Gahm to fetch the first column col in the SELECT statement should be the first column or at least a part of the primary key to avoid reading many blocks at database level.

Like 0 Share. Right click and copy the link to share this comment. Horst Keller Blog Post Author. Former Member. Like 1 Share. Rakshith Gore. Hi Rakshit, transporting a fixed single character value from database to server should be the fastest thing you can do. Raghu Govindarajan. Joachim Rees. Forwarded to development and under discussion Like 2 Share.

Eng Swee Yeoh. Hi Horst I just have to ask. Regards Eng Swee. Hi Shai, Armin Thank you for your replies. I think the cost is only relevant when a full key is not specified. Regards Eng Swee PS: Don't have developer key at my current role so can't do the performance comparison myself. Hope this helps I have posted my raw results in a google sheet Raghu. What I'm wondering about Isn't the performance of a mass access much more important? So, if you have mass existence checks, Ok, but otherwise, hmm.

What do you think? Kiran K. Exactly, 2 seconds delay matter a lot in such instance. Thanks Horst, for sharing your expertise. Thanks for your contributions! So glad I found this blog again, to look up on this issue.

Best Joachim. Horst Keller How about now, 2 Years later? Abdul Hakim. Hi Horst, Thanks for sharing this blog with the community. Thanks, Abdul Hakim.

Thanks Keller this blog helpfull to understand select query. It's quite bad from performance perspective. Please avoid it. How do you determine this result?

To 1 : Of course you fetch data, at least your database do it because it has to count rows. Horst Keller wrote Ooops, right. Horst Keller wrote: Ooops, right. Mark Rotteveel Klapsius Klapsius 3, 6 6 gold badges 27 27 silver badges 51 51 bronze badges.

Just reference the primary key for the table in your WHERE clause - the one thing that uniquely references and identifies each row in your table Not possible in your case. Add a comment. Active Oldest Votes. Improve this answer. Reason for that is backward compatibility.

This should no longer considered to be the answer. Also in that answer you can find two solutions including TOP syntax that you mentioned in your quote.

Jerry Jerry 1. Welcome to Stack Overflow. Code-only answers are strongly discouraged. Please include an explanation of how and why this solves the problem.

This will help future readers to better understand your solution.