Module 10
Merging Data and Passing
Tables
Module Overview
• Using the MERGE Statement
• Implementing Table Types
• Using Table Types As Parameters
Lesson 1: Using the MERGE Statement
• MERGE Statement
• WHEN MATCHED
• WHEN NOT MATCHED BY TARGET
• WHEN NOT MATCHED BY SOURCE
• OUTPUT Clause and $action
• MERGE Determinism and Performance
• Demonstration 1A: MERGE Statement
MERGE Statement
• Modifies data in a target table (or updatable view or CTE) based
on the results of a join with a source table
• Commonly used to populate data warehouses

INSERT data if not already present

UPDATE data if already present
• Target table plus a source rowset
• Must specify how the source and target are joined
MERGE INTO dbo.Employee AS e
USING dbo.EmployeeUpdate AS eu
ON e.EmployeeID = eu.EmployeeID
…
WHEN MATCHED
• Clause that defines the action to be taken when the row in the
source is found in the target
• Specifies the data modifications to take place – can be INSERT,
UPDATE or DELETE
• Two WHEN MATCHED clauses can be included – needs an extra
predicate on the first

WHEN MATCHED AND s.Quantity > 0

One must be an UPDATE, the other a DELETE
MERGE INTO dbo.Employee AS e
USING dbo.EmployeeUpdate AS eu
ON e.EmployeeID = eu.EmployeeID
WHEN MATCHED THEN
UPDATE SET e.FullName = eu.FullName,
e.EmploymentStatus = eu.EmploymentStatus
WHEN NOT MATCHED BY TARGET
• Clause that defines the action to be taken when the row in the
source cannot be found in the target
• The words BY TARGET are optional and often omitted
MERGE INTO dbo.Employee AS e
USING dbo.EmployeeUpdate AS eu
ON e.EmployeeID = eu.EmployeeID
WHEN MATCHED THEN
UPDATE SET e.FullName = eu.FullName,
e.EmploymentStatus = eu.EmploymentStatus
WHEN NOT MATCHED THEN
INSERT (EmployeeID,FullName,EmploymentStatus)
VALUES
(eu.EmployeeID,eu.FullName,eu.EmploymentStatus);
WHEN NOT MATCHED BY SOURCE
• Clause that defines the action to be taken for rows in the target
that were not supplied in the source
• Not commonly used but typically involve a DELETE
MERGE INTO dbo.Employee AS e
USING dbo.EmployeeUpdate AS eu
ON e.EmployeeID = eu.EmployeeID
WHEN MATCHED THEN
UPDATE SET e.FullName = eu.FullName,
e.EmploymentStatus = eu.EmploymentStatus
WHEN NOT MATCHED THEN
INSERT (EmployeeID,FullName,EmploymentStatus)
VALUES
(eu.EmployeeID,eu.FullName,eu.EmploymentStatus)
WHEN NOT MATCHED BY SOURCE THEN
DELETE;
OUTPUT Clause and $action
• OUTPUT clause can also be used with MERGE
• $action used to determine the action taken for each row
MERGE INTO dbo.Employee AS e
USING dbo.EmployeeUpdate AS eu
ON e.EmployeeID = eu.EmployeeID
WHEN MATCHED THEN
UPDATE SET e.FullName = eu.FullName,
e.EmploymentStatus = eu.EmploymentStatus
WHEN NOT MATCHED THEN
INSERT (EmployeeID,FullName,EmploymentStatus)
VALUES
(eu.EmployeeID,eu.FullName,eu.EmploymentStatus)
OUTPUT
$action,inserted.EmployeeID,deleted.EmployeeID;
MERGE Determinism and Performance
• Matching source and destination rows using MERGE is not
the same as matching with UPDATE
• UPDATE can allow a source row to update multiple target
rows
• MERGE joins must be deterministic – an incoming row
must only match a single target row
• MERGE performs well as it makes only a single pass
through the data

Often better performance than separate INSERT, UPDATE and
DELETE statements
Demonstration 1A: MERGE Statement
In this demonstration you will see:
• How to use the MERGE statement
• How to use the OUTPUT clause with the MERGE statement
• How to perform optional updates with MERGE
• How to use MERGE as a composable query
• How to use the VALUES clause as a MERGE source
Lesson 2: Implementing Table Types
• Reducing Round-Trip Overhead
• Options for Passing Lists as Parameters
• Demonstration 2A: Passing Delimited Lists
• Introduction to the TABLE Type
• Populating TABLE Types with Row Constructors
• Demonstration 2B: TABLE Types and Row Constructors
Reducing Round-Trip Overhead
• Round-trip to from an application to SQL Server and back
can be substantial

Common aim to minimize the impact of round trips
• Many operations include many round-trips and cause
transactions to last longer than desirable
• Add an order

Start Transaction

Save Order Header

Save Order Detail Line 1

Save Order Detail Line 2

Save Order Detail Line 3

Commit Transaction
Options for Passing Lists as Parameters
• Prior to SQL Server 2008, options for passing lists of
values in a single call were limited
• Delimited Lists (often comma-delimited)

Required writing custom parsing logic

Loose structure

Loose data typing
• XML

Also requires some complex parsing logic

Semi-structured

Loose data typing without schemas
Demonstration 2A: Passing Delimited Lists
In this demonstration, you will see
• How to query a table-valued function that performs list
parsing
• How the function allows for different delimiters
• How to use the function in a join
• How common errors can occur with delimited lists
Introduction to the TABLE Type
• Earlier versions of SQL Server allowed variables to be of type
TABLE and to allow definition of the structure of the table
• SQL Server allows the creation of table data type definitions

Can be used for variables

Can be used for parameters
CREATE TYPE dbo.CustomerBalance
AS TABLE ( CustomerID int,
CurrentBalance decimal(18,2));
GO
Populating TABLE Types with Row Constructors
• SQL Server allows the population of multiple rows of data into a
table variable via row constructors

Can be used with both INSERT and MERGE statements
• Multi-row inserts are atomic operations

All inserts occur or none occur
DECLARE @Balance dbo.CustomerBalance;
INSERT INTO @Balance
VALUES (12,14.50),(15,13.75),(22,19.50);
Demonstration 2B: TABLE Types and Row Constructors
In this demonstration you will see:
• How to work with row constructors
• How to declare a table data type
• How to work with variables with user-defined table data
types
Lesson 3: Using TABLE Types As Parameters
• TABLE Input Parameters for Stored Procedures
• Using Row Constructors to Populate Parameters
• Demonstration 3A: Passing Tables to Stored Procedures
TABLE Input Parameters for Stored Procedures
• User-defined table data types can be used as input parameters
for stored procedures
• Not able to be used for output parameters
• Must include READONLY in the definition
CREATE TYPE dbo.SalesDetails AS TABLE
( Description varchar(50),
Price decimal(18,2)
);
GO
CREATE PROCEDURE dbo.SalesInsert
@CustomerID int,
@PurchaseOrderNumber varchar(20),
@SalesDetails dbo.SalesDetails READONLY,
@SaleID int OUTPUT
AS BEGIN
Using Row Constructors to Populate Parameters
• Table variables are created to provide the parameters to pass to
stored procedures with table-valued parameters
• Row constructors are ideal for populating the table variables prior
to making the stored procedure call
DECLARE @SaleID int;
DECLARE @SalesDetails dbo.SalesDetails;
INSERT INTO @SalesDetails
VALUES('Product 1',12.3),
('Product 2',14.66),
('Product 3',122.35);
EXEC dbo.SalesInsert
12,'BigOrder',@SalesDetails,@SaleID OUTPUT;
Demonstration 3A: Passing Tables to Stored Procedures
In this demonstration you will see:
• How traditional stored procedure calls often involve
multiple round trips to the server
• How to declare a table data type
• How to use the table data type to avoid round trips
• How to view catalog information about the table data
types by querying the sys.types and sys.table_types
system views
Lab 10: Passing Tables and Merging Data
• Exercise 1: Create a Table Type
• Exercise 2: Use a Table Type Parameter
• Challenge Exercise 3: Use a Table Type with MERGE (Only
if time permits)
Logon information
Virtual machine
623XB-MIA-SQL
User name
AdventureWorks\Administrator
Password
Pa$$w0rd
Estimated time: 45 minutes
Lab Scenario
In earlier versions of SQL Server, passing lists of values to
stored procedures was a challenge. SQL Server 2008
introduced the table type and table-valued parameters. In
this lab, you will create a replacement stored procedure
Reports.GetProductsByColorList_Test that uses a tablevalued parameter to replace an existing stored procedure
Reports.GetProductsByColorList that was based on passing
a comma-delimited list of values.
You will then create a new procedure that processes
complete rows of data and performs updates using the
MERGE statement.
Lab Review
• What is the purpose of the OUTPUT clause?
• In the values returned by an OUTPUT clause, how can we
tell if an INSERT, UPDATE or DELETE occurred?
Module Review and Takeaways
• Review Questions
• Best Practices