1. Boost your T-SQL with the APPLY Operator
Itzik Ben-Gan | T-SQL Trainer and Co-founder, SolidQ
Umachandar Jayachandran (UC) | Program Manager, Microsoft

2. Meet Itzik Ben-Gan | ‏@ItzikBenGan
T-SQL Trainer and Co-founder, SolidQ
Delivering T-SQL training around the world (
Author of many T-SQL books
Columnist, SQL Server Pro Magazine
Regular speaker at events like SQL PASS and Dev Connections
Over two decades of experience with SQL and databases

3. Meet Umachandar Jayachandran (UC)
Program Manager, Microsoft
SQL Server Product Group
Worked on SQL Server since 2008 release
Currently working on Windows Azure SQL Database
Have worked with databases (Sybase, Oracle & SQL Server) since 1998
Microsoft representative for ANSI SQL standards group

4. Course Topics Boost your T-SQL with the APPLY Operator
01 | APPLY, Described
02 | APPLY Boosts various T-SQL Features

5. Setting Expectations Target Audience
T-SQL practitioners with at least half a year of experience
Suggested Prerequisites/Supporting Material
Microsoft SQL Server 2012 T-SQL Fundamentals (MSPress, 2012)
Source code:
Few leading slides – mostly T-SQL coding demos!

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7. 01 | APPLY, Described
Itzik Ben-Gan | T-SQL Trainer and Co-founder, SolidQ
Umachandar Jayachandran (UC) | Program Manager, Microsoft

8. Module Overview
Joins vs. APPLY
CROSS APPLY
OUTER APPLY
Implicit APPLY

9. Joins vs. APPLY Cross Join Inner Join APPLY (2005+)
Both input sets predefined (pre-operator treatment), Result: all combinations
Inner Join
Both input sets predefined, Result: only matching combinations
APPLY (2005+)
Left input set predefined, Right set evaluated per left row using correlations Result: unified results of evaluations X
All
Combinations
X + ?
Matching
Combinations 1 2
Unified Results

10. CROSS APPLY Apply right set per left row using correlations
Left rows discarded if right side is empty
SELECT C.custid, C.companyname, O.orderid, O.orderdate, O.empid
FROM Sales.Customers AS C
CROSS APPLY dbo.GetTopOrders(C.custid, 3) AS O;

11. OUTER APPLY Apply right set per left row using correlations
Left rows preserved when right side is empty NULLs used as placeholders
SELECT C.custid, C.companyname, O.orderid, O.orderdate, O.empid
FROM Sales.Customers AS C
OUTER APPLY dbo.GetTopOrders(C.custid, 3) AS O;

12. Implicit APPLY
Refer to a table UDF in subquery Pass columns from outer table as inputs (correlations)
SELECT C.custid, C.companyname,
(SELECT COUNT(DISTINCT empid)
FROM dbo.GetTopOrders(C.custid, 3) AS O) AS numemps
FROM Sales.Customers AS C;