A number of business processes require you to distribute a value over a date range. However, if your distribution keys and values don’t add up perfectly or aren’t perfectly divisible, it’s very easy to get rounding errors in your distributions.Continue reading
There’s more to the VALUES clause in T-SQL than meets the eye. We’ve all used the most basic INSERT syntax:
INSERT INTO #work (a, b, c) VALUES (10, 20, 30);
But did you know that you can create multiple rows using that same VALUES clause, separated by commas?
INSERT INTO #work (a, b, c) VALUES (10, 20, 30), (11, 21, 31), (12, 22, 32);
Note the commas at the end of each line, denoting that a new row begins here. Because this runs as a single statement, the INSERT runs as an atomic operation, meaning that all rows are inserted, or none at all (like if there’s a syntax issue or a constraint violation).
I use this construct all the time to generate scripts to import data from various external sources, like Excel, or even a result set in Management Studio or Azure Data Studio.
Here’s something you can try:
- Select a dataset from SSMS or Excel, copy it to the clipboard, and paste it into a new SSMS window.
- Select just one of the tabs, then use the “find and replace” feature (Ctrl+H) in SSMS to replace all tabs with the text
', '(including the apostrophes).
- Now, add the text
('at the beginning of each line and
'),at the end of each line. The last line obviously won’t need the trailing comma. If you’re handy with SSMS, you can do at least the leading values with a “box select”: holding down the Alt key as you make a zero-width selection over all the rows, then typing the text.
If all of this sounds like a lot of work for you, you might want to try out a little web hack that I wrote. It allows you to paste a tab-delimited dataset, just like the ones you get from Excel or the result pane in SSMS or ADS, into a window and instantly convert it into a T-SQL INSERT statement with the click of a button.
Pro tip: in SQL Server Management Studio, use Ctrl+Shift+C to copy not only the results, but also the column names!
- First row has headers: instead of inserting the first row of the raw data, the script uses it to map the INSERTed values to the correct columns in the destination table.
- Fix nulls: Particularly when exporting from SSMS, we’ll lose information about which values are actually NULL and which ones are actually the text “NULL”. When this option is unchecked, the values will be treated as the text “NULL”, when checked, all values that consist entirely of the text “NULL” will have the surrounding apostrophes removed, so they become actual NULL values.
- Pretty: adds some indenting spaces to the output code. This increases the script size by a few bytes, but increases readability.
- Table name: Option table name to put in the INSERT INTO header of the script.
And to make sure you sleep well at night, the entire process on table.strd.co happens in the browser – nothing is ever uploaded to the Internet.
Here’s a quick tip that touches on one of the powerful SSMS tricks in my “Management Studio Level-Up” presentation. Say you have a potentially large number of database objects (procedures, functions, views, what have you), and you need to make a search-and-replace kind of change to all of those objects.
You could, of course, put the database in source control and use a proper IDE to replace everything, then check your code back into source control and commit it to the database. That’s obviously the grown-up solution. Thanks for reading this post.
But let’s say for the sake of argument that you haven’t put your database in version control. What’s the lazy option here?Continue reading
Date and time values are not entirely intuitive to aggregate into averages in T-SQL, although the business case does arguably exist. Suppose, for instance, that you have a production log with a “duration” column (in the “time” datatype), and you want to find the totalt or average duration for a certain group of items.
It’s possible, but I would still call it a workaround.Continue reading
I’ve been working on a little gadget for a while now, and today I finally got around to completing it and so now I’ve published it for everyone to try out. It’s a web API (wait, wait, don’t go away – it’s for database people!) that creates a randomized list of names, addresses, etc.
In this post, I’ll show you how easy it is to use this service to anonymize a development or test database so you don’t have all that personally identifiable information floating around.Continue reading
I came upon this issue when I was building some views to support legacy integrations to an app that I was refactoring. The view is supposed to have exactly the same column definitions as a table in the old database that I am redesigning, so to make SSIS packages and other integrations run smoothly, I want the view’s columns to have the same datatypes, nullability, etc.
But there are some gotchas to watch out for with CAST and CONVERT.Continue reading
You may think that speaking at usergroups and conferences is reserved for a select group of elite professionals. Let me tell you right away that this is not the case, and that you should seriously consider a rewarding side career as a speaker at usergroups and conferences!
Here’s the why and the how.
Typically, the advice on fill factor is “if it ain’t broke, don’t fix it”. But occasionally, you’ll find a database or even a server with a crazy default setting that just fills your disk and buffer pool without any real benefit. Here’s a nifty script to rebuild any tables and indexes to a fill factor of 100%.
Here are 50 random numbers:
--- 50 random numbers WITH cte AS ( SELECT 0 AS i, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) AS n UNION ALL SELECT i+1, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) FROM cte WHERE i<50) SELECT * FROM cte;
And in SSMS, with the variable-width default font, the output looks… slightly-less-than-readable in the grid view:
We could use STR() to format the output, but the indent looks a little off:
--- 50 random numbers WITH cte AS ( SELECT 0 AS i, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) AS n UNION ALL SELECT i+1, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) FROM cte WHERE i<50) SELECT *, STR(n, 12, 2) AS with_str FROM cte;
Here’s something I’ve found: the space character is roughly about half the width of a typical number character. So replace every leading space with two spaces, and it will look really neat in the grid:
--- 50 random numbers WITH cte AS ( SELECT 0 AS i, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) AS n UNION ALL SELECT i+1, 100000.*POWER(RAND(CHECKSUM(NEWID())), 3) FROM cte WHERE i<50) SELECT *, STR(n, 12, 2) AS with_str, REPLACE(STR(n, 12, 2), ' ', ' ') AS with_replace FROM cte;
(and terrible everywhere else, obviously.)
Download and print this nifty little PDF with all of the INNER, LEFT, RIGHT, FULL and CROSS JOINs visualized! It’ll look great on your office wall or cubicle. Your coworkers and your interior decorator will love you for it.
How it works: For each join example, there are two tables, the left and the right table, shown as two columns. For the sake of simplicity, these tables are called “a” and “b” respectively in the code.
You’ll notice that the sheet uses a kind of pseudo-code when it comes to table names and column names.