SQL Server - Bài 6

Stored Procedures &
User-Defined Functions
Vu Tuyet Trinh

Hanoi University of Technology
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Introduction to SQL Batch Processing
Batch
Individual SQL
commands
Grouped to form a
batch
Compiled
as single
execution
plan
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Example
Use Pubs
Select * from authors
Update authors
set phone= '890 451-7366‘
where au_lname= 'White'
Go
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Outline
√
Understanding the concepts of batch and batch
processing


T-SQL Programming

Define and assign variables

Cursors for data retrieval

Control statements

Write SQL statements using SQL Server basic functions

Use basic functions in a query

Implementing Stored Procedures

Implementing User-Defined Functions
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Assigning values to variables

SET statement
SET @local_variable name = value


SELECT statement
SELECT @local_variable name = value

Example
SET @CUST=’FRANK’
SELECT CUSTOMERID,COMPANYNAME
FROM CUSTOMERS

WHERE CUSTOMERID = @CUST
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Variables
SQL Server supports two types of variables in T-SQL
@@global_variable
@local_variable
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List of Global variables
@@CONNECTIONS Number of connections made to the server
since it was last started.
@@CPU_BUSY Number of milliseconds the system has been
processing since SQL Server was started
@@CURSOR_ROWS Number of rows in the most recently opened
cursor.
@@ERROR Error number of the last T-SQL error
@@FETCH_STATUS 0 if the last fetch status was successful.
-1 if there was an error
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List of Global variables (2)
@@IDENTITY Last inserted identity value
@@LANGUAGE Name of the language currently in use.
@@MAX_CONNECTIONS Maximum number of concurrent
connections that can be made.
@@ROWCOUNT Number of rows affected by most
recent SQL Statement
@@SERVERNAME Name of local server
@@SERVICENAME Name of the SQL Service on this
computer
@@TIMETICKS Number of microseconds per tick on
the current computer

@@TRANSCOUNT Number of transaction open on the
current connection
@@VERSION Version information of SQL Server
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Cursors to Retrieve Data

Allowing positioning at specific rows of the result set

Retrieving one row or block of rows from the current
position in the result set

Supporting data modifications to the rows at the current
position in the result set

Supporting different levels of visibility for changes made
by other users to the data in the result set

Providing access to the data in a result set for T-SQL
statements in scripts, stored procedures, and triggers
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Cursor Implementations

Transact-SQL Server Cursors

Used in scripts, stored procedures, and triggers

Implemented on the server

API Server Cursors


Implemented on the server but managed by API cursor
functions (OLE DB, ODBC, DB-Library)

Client Cursors

Entire result set is cached on client and all cursor
operations are performed against this cached set
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Working with T-SQL Server Cursors

Declare the cursor

Populate the cursor

Retrieve (fetch) the result set

First, Next, Prior, Last, Absolute n, Relative n

Optional: update or delete a row

Close the cursor

Free resources allocated to the cursor
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Control Statements
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Control Statements Contd…
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BEGIN..END
A set of TSQL statements to be executed can be enclosed in

BEGIN..END.
Syntax:
BEGIN
{ statement | statement_block}
END
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IF..ELSE
We can execute different
sets of SQL statements based on
specified conditions.
Syntax:
IF Boolean_expression

{ sql_statement |
statement_block }
[ ELSE
{ sql_statement |
statement_block } ]
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Example