1. Cleveland SQL Saturday Catch-All or Sometimes Queries
Michael John 1

2. Cleveland SQL Saturday
About Me!
8th SQL Saturday
20 years as a developer, DBA, and general IT pain.
Started with SQL 6.0
Became the DBA because I was the only person who knew “SELECT * FROM TABLE”
First job in IT was an entry level developer at 17k per year.
Three years later I was Director of IT with a staff of 45. Making a little more than 17k!
I wish I had more time to write again.
And more money for longer vacations!
Been there, done that! 2

3. Cleveland SQL Saturday What I spend all my time on!3

4. Cleveland SQL Saturday My Rants
Triggers
Cursors
Cryptcnmes
Doing work on a production machine
A server is NOT a desktop!!!
Begging for disk space
Untested code / procedures being run in production. “Google programming”
Copy and paste coding practices
Just because you can, doesn’t mean you should.
Incompetence being touted as authority 4

5. Cleveland SQL Saturday
SQL Saturday 2015, October 3rd.
Is promoting a Pittsburgh function something that’s allowed in Cleveland? 5

6. Cleveland SQL Saturday Agenda
What are catch-all queries?
Examples
Issues
How to handle them
Bad Practices
Questions, and maybe correct answers 6

7. Cleveland SQL Saturday
What are Catch-All Queries?
The term was coined by Gail Shaw in the article on her web site.
This presentation acknowledges this article as a source. 7

8. Cleveland SQL Saturday What are Catch-All Queries?
Queries that contain many optional parameters
Queries that run in many different ways, depending upon the parameters
Plan cache is likely less than optimal
Typically the back end to a search screen
Reporting Reporting Reporting 8

9. Cleveland SQL Saturday What Are Catch-All Queries?
They are also hidden by developers
If you see a proc with…
= something BEGIN
--Do some select
= something else BEGIN
--Do some other select
Converting a procedural query to a set based query may create a catch-all 9

10. Cleveland SQL Saturday What are Catch-All Queries?
Reports that have many parameters
All, one, or many values
Customers
Date Ranges
Status list
Any number of other values
Look for reports with drop downs that contain “ALL”, “None”, and so forth as a value that can be selected 10

11. Cleveland SQL Saturday What are Catch-All Queries?11

12. Cleveland SQL Saturday Example of a catch-all query
This is an actual example from my current system
Example #2 12

13. Cleveland SQL Saturday What issues do they cause???
Many possible execution plans, the best one may not be used.
Table scans, table scans, table scans, depending how its written
Larger tables, large result sets, or a high number of executions may be very slow.
User complain. It’s too (fill in the blank)
Difficult to maintain
Code may be hard to follow 13

14. Cleveland SQL Saturday
How do we handle them???
You don’t. You can only lessen the pain!
Seriously re-consider the architecture
Was this ever planned for in the first place?
Did this evolve over time? User requests?
Do the business rules still apply? “It’s the way we always did it”
Are there other methods that may work better?
Full-Text search? Lucene?
Create big old denormalized tables
Create big “word lists”
Data warehouse?
Do this in code, not T-SQL?
Do these need to be real time?? 14

15. Cleveland SQL Saturday
How do we handle them???
DO NOT WRITE CODE, CHANGE INDEXES, OR FIX SETTINGS AS YOUR FIRST STEP
Find the pattern. Understand what is happening.
Capture values of the parameters over a period of time
Example #3
Capture the performance over time. Correlate this to the parameters being used.
Mornings? Afternoons? End of the month?
Example #3a.xls
Determine the net effect of a change!!!!!
Execution time is all that really matters 15

16. Cleveland SQL Saturday
How do we handle them???
From the analysis…
Only certain people or locations use specific features. User training!
Majority of the searches are on a single field, which comes from one location
This was never in the original design, it evolved
What the users really want is a Google-like search or an “incremental” search
Almost HALF of the executions that occur on this screen can be replaced by a report. They pick a wide open search, and export it into a spreadsheet. 16

17. Cleveland SQL Saturday
How do we handle them???
Actions
This is being broken into 2 separate screens, 2 reports were also developed
The Google-like search is being implemented with full text search
A complete result set will be pulled into a “cache” and the heavy lifting will be done in code (Maybe!)
Lots of user training! 17

18. Cleveland SQL Saturday How to handle them. Method #1
WHERE clause
WHERE field) = field
Really a bad way to do this.
NON-SARGABLE
Likely a table scan
Example #4 18

19. Cleveland SQL Saturday How to handle them. Method #2
Select it all into a temp table, delete what you don’t need.
Works pretty well for a small result set
Performs poorly with larger results or frequent executions
IO, IO, it’s off to work we go!
It just looks funny!!!!
Example #5 19

20. Cleveland SQL Saturday How to handle them. Method #3
Create different procedures for the different combinations
Good performance
Bad for maintenance
Example #6 20

21. Cleveland SQL Saturday
How to handle them. Method #4  
Use the data you collected, create different procedure(s) for the most used combinations
Something else for the rest
If you need to do this, you are going to wait
Good performance
Bad maintenance
Example #6X 21

22. Cleveland SQL Saturday
How to handle them. Method #5  
Table Variables / AND EXISTS
Useful in reporting scenarios
Example #7 22

23. Cleveland SQL Saturday
How to handle them. Method #6  
For numeric types, set a number value that works for the different possibilities
NULLS will not work
Handle this in a subquery, depending upon the situation
Can be a bit hard to understand
Example #8 23

24. Cleveland SQL Saturday
How to handle them. Method #7  
MIN/MAX/BETWEEN
NULLS will not work
Handle this in a subquery, depending upon the situation
Can be a bit hard to understand
Example #8A 24

25. Cleveland SQL Saturday
How to handle them. Method #8  
MIN/MAX/BETWEEN/CHECKSUM
NULLS will not work
Handle this in a subquery, depending upon the situation
Can be a bit hard to understand
Example #8B 25

26. Cleveland SQL Saturday
How to handle them  Method #8
Think outside the box and change the rules!
Example #XXX 26

27. Cleveland SQL Saturday
How to handle them. Method #9 
Dynamic SQL
Example #9 and 9a 27

28. Cleveland SQL Saturday
How to handle them. Method #10 
Whatever works best
Example #11 28

29. Cleveland SQL Saturday
Take Aways 
Determine the pattern
Gather the FACTS
Make a decision
Be prepared to change
Be prepared to be challenged 29

30. Cleveland SQL Saturday
Questions? Suggestions?  30