SQL Tip: Windowing Functions

A simple SELECT returns all relevant rows from the database. GROUP BY applies aggregate functions, condensing SELECTed data into one summary row per grouping. What if mixing the two approaches is desired—what if data rows need to be combined with aggregate totals in the same result set?

T-SQL’s OVER clause allows several kinds of functions to be applied to non-GROUPed BY rows. Using OVER, a simple SELECT returning data rows can be expanded to include columns containing summary statistics. Traditionally, aggregate functions can only be used in conjunction with GROUP BY or to produce a single row summary result set; when used with OVER, these limitations are removed. Continue reading

Understanding MaximumErrorCount

Learning about how SSIS’s MaximumErrorCount property works can be challenging. There’s not much documentation describing this property and the behavior it controls. Here’s my attempt to help remedy this.


MaximumErrorCount

When the number of errors occurring inside a container during execution reaches its MaximumErrorCount, the container’s ExecutionResult is changed to Failure if it is not already set to that state. A value of zero sets the error count threshold to infinity, disabling this functionality. Continue reading

SSRS: Auditing Report Queries

Want to view a list of queries used in reports deployed on a Microsoft SQL Server Reporting Services (SSRS) server?

While SSRS’s web service exposes the functionality necessary to assemble this information, using that service requires programming/scripting skills or third-party software. Thankfully, these requirements can be bypassed by fetching this information directly from the report server database. Continue reading

ETL Without the T: A Loop-Driven, Data about the Dataflow Approach Using SSIS

Microsoft SQL Server Integration Services (SSIS) is designed for ETL. However, sometimes the T in ETL isn’t necessary: data simply needs to be moved without manipulation. While defining a simple source-to-destination dataflow is easy, filling a package with the numerous copy operations required to move data between multiple source-destination pairs results in a verbose package that violates the Don’t Repeat Yourself (DRY) principle.

Using a loop to apply a single copy data dataflow to a list of source-destination pairs eliminate this negative. With this approach, the main dataflow in the SSIS package is not the data being moved; rather, it is data about that data—that is, data describing the sources and destinations to which the extract-and-load operation should be applied. Continue reading

SQL Tip: Breaking into Batches

Internet search results are typically broken into batches. The initial page displays results 1 through perhaps 10, page two shows matches 11–20 and so on. Splitting results up like this is known as (no surprise) paging.

To implement results paging with Microsoft SQL Server (version 2012 or later), try modifying your ORDER BY clause with OFFSET and FETCH. OFFSET tells SQL Server to start returning x rows into a result set. FETCH defines the number of rows to return. Continue reading

SQL Tip: Adjusting Alphabetization

Alphabetical sorting is simple: A comes after B, next comes C, then D and so on all the way to Z…right?!

If only it were so easy! Consider the character Á—should it be sorted before A, after A or just like it was A (ignoring the accent)? The answer depends on language: Hungarian’s Á comes after A; in Spanish, the accent should be ignored. In many languages, Y comes between X and Z; however, Lithuanian orders Y before J. French has an interesting twist: sometimes strings are sorted by first comparing their letters from left to right then by comparing diacritics from right to left. Some languages even treat certain multi-character combinations as single letters, like CD in Welsh. If this doesn’t sound complex enough, alphabetization rules can change: for example, in 1994, the Congress of the Association of Spanish Language Academies decreed that Spanish’s CH would no longer be considered a single, muilt-character letter combination! Continue reading