SQL Server 2008, SQL Server 2005, SQL Server 2003, SQL Azure, Oracle Tutorials

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SQL Server 2008 R2 : Transactions and Batches

There is no inherent transactional quality to batches. As you have seen already, unless you provide the syntax to define a single transaction made up of several statements, each individual statement in a batch is its own separate transaction, and each statement is carried to completion or fails individually.

SQL Server 2008 R2 : Defining Transactions

The terms for explicit and implicit transactions can be somewhat confusing. The way to keep them straight is to think of how a multistatement transaction is initiated, not how it is completed. AutoCommit transactions are in a separate category because they are both implicitly started and committed.

MySQL Replication for Scale-Out : Consistency in a Hierarchal Deployment

Managing consistency in a hierarchal deployment is significantly different from managing consistency in a simple replication topology where each slave is connected directly to the master.

MySQL Replication for Scale-Out : Managing Consistency of Data

One of the problems with asynchronous replication is managing consistency. To illustrate the problem, let’s imagine you have an e-commerce site where customers can browse for items they want to purchase and put them in a cart.

SQL Server 2008 : Security - SQL injection protection

The semicolon character marks the end of one command. The rest of the input will run as a separate query, and by adding the comments (--) characters to the end of the input, we ensure any code added to the end of the variable will be ignored, thus increasing the chances of running the injected code.

SQL Server 2008 : Security - Data encryption

SQL Server 2005 introduced the ability to encrypt data at rest, meaning data stored within the database itself. Known as cell-level encryption, this was a welcome addition to the other encryption features in earlier versions that allowed encryption of data in transit, such as network encryption with SSL.

MySQL Replication for Scale-Out : Specialized Slaves

In the simple scale-out deployment—like the one described thus far—all slaves receive all data and can therefore handle any kind of query. It is, however, not very common to distribute requests evenly over the different parts of the data. Instead, there is usually some data that needs to be accessed very frequently and some that is rarely accessed.

MySQL Replication for Scale-Out : Hierarchal Replication

Although the master is quite good at handling a large number of slaves, there is a limit to how many slaves it can handle before the load becomes too high for comfort (a user mentioned 70 slaves as a practical limit for his purposes, but as you probably realize, this depends a lot on the application), and an unresponsive master is always a problem.

SQL Server 2008 R2 : Creating and Managing Triggers - Using Nested Triggers, Using Recursive Triggers

Triggers can be nested up to 32 levels. If a trigger changes a table on which another trigger exists, the second trigger is fired and can then fire a third trigger, and so on. If the nesting level is exceeded, the trigger is canceled, and the transaction is rolled back.

SQL Server 2008 R2 : Creating and Managing Triggers - Using CLR Triggers

CLR triggers are triggers based on the CLR. CLR integration, which was added with SQL Server 2008, allows for database objects (such as triggers) to be coded in one of the supported .NET languages, including Visual Basic .NET and C#.

SQL Server 2008 R2 : Security - Auditing (part 2) - DDL triggers, Logon triggers, Change Data Capture

In a manner similar to creating DDL triggers, you create a logon trigger to either roll back (deny) a logon or capture information surrounding the logon using the EVENTDATA function.

SQL Server 2008 R2 : Security - Auditing (part 1) - SQL Server Audit

In SQL Server 2005 and earlier, auditing options consisted of simple server-level logon success/failure logging, custom audits using server-side traces or SQL Profiler, or the C2 trace option.

SQL Server 2008 R2 : Using DML Triggers (part 5) - Cascading Updates, INSTEAD OF Triggers

SQL Server 2000 introduced a type of trigger called an INSTEAD OF trigger. This type of trigger extends SQL Server’s trigger capabilities and provides an alternative to the AFTER trigger that was heavily utilized in prior versions of SQL Server.

SQL Server 2008 R2 : Using DML Triggers (part 4) - Enforcing Referential Integrity by Using DML Triggers, Cascading Deletes

In a database environment in which multiple databases are used with related data, a trigger can be invaluable for enforcing referential integrity. The trigger can span databases, and it can ensure that data rows inserted into a table in one database are valid based on rows in another database.

SQL Server 2008 R2 : Using DML Triggers (part 3) - Using inserted and deleted Tables

In most trigger situations, you need to know what changes were made as part of the data modification. You can find this information in the inserted and deleted tables. For the AFTER trigger, these temporary memory-resident tables contain the rows modified by the statement.

SQL Server 2008 R2 : Using DML Triggers (part 2) - Using AFTER Triggers

An AFTER trigger is the original mechanism that SQL Server created to provide an automated response to data modifications. Prior to the release of SQL Server 2000, the AFTER trigger was the only type of trigger, and the word AFTER was rarely used in its name.

SQL Server 2008 R2 : Using DML Triggers (part 1) - Creating DML Triggers

You can create and manage triggers in SQL Server Management Studio or directly via Transact-SQL (T-SQL) statements. The Object Explorer in SSMS provides a simple means of creating triggers that you can use to generate the underlying T-SQL code.

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 6) - Rewriting Stored Procedures as Functions, Creating and Using CLR Functions

Prior to SQL Server 2005, the only way to extend the functionality of SQL Server beyond what was available using the T-SQL language was to create extended stored procedures or Component Object Model (COM) components.

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 5) - Viewing and Modifying User-Defined Functions - Using T-SQL to Modify Functions, Using SSMS to View and Modify Functions

If the function you want to view or edit is not shown in the list, it was probably created after the list of functions in the Object Explorer was populated. You might need to refresh the function list in Object Explorer. To do this, you right-click the Functions folder and choose Refresh.

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 4) - Viewing and Modifying User-Defined Functions - Using T-SQL to View Functions

Besides using T-SQL commands to create functions, you can also use them to view and modify functions. You can get information by using the provided system procedures and queries against the INFORMATION_SCHEMA.routines view. The following sections describe these methods.

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 3) - Creating User-Defined Functions - Creating Custom Function Templates

To create a custom function template, right-click the Function folder in the Template Explorer and select New. SSMS then creates an entry in the Template Explorer, and you can specify the name for the template, as shown in Figure 4.

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 2) - Creating User-Defined Functions - Using SSMS to Create Functions

To create a function by using SSMS, open the Object Explorer to the database in which you want to create the function. Then select the Programmability node, right-click the Functions node, select New, and then choose one of the three available options as shown in Figure 1:

SQL Server 2008 R2 : Creating and Managing User-Defined Functions (part 1) - Creating User-Defined Functions - Creating T-SQL Functions

If you choose to encrypt the function code, you should be sure to save a copy of the script used to create the function to a file outside the database, in case you ever need to modify the function or re-create it. After the source code for the function is encrypted, you cannot extract the original unencrypted source code from the database.

SQL Server 2008 R2 : Types of User-Defined Functions

A scalar function is like the standard built-in functions provided with SQL Server. It returns a single scalar value that can be used anywhere a constant expression can be used in a query. (You saw an example of this in the earlier description of the getonlydate() function.)

SQL Server 2008 R2 : Why Use User-Defined Functions?

The main benefit of user-defined functions is that they mean you are not limited to just the functions SQL Server provides. You can develop your own functions to meet your specific needs or to simplify complex SQL code.

SQL Server 2008 : Security - Implementing least privilege (part 2) - Role-based security

When discussing security in SQL Server, the terms principal and securable are commonly used. A principal is an entity requesting access to SQL Server objects (securables). For example, a user (principal) connects to a database and runs a select command against a table (securable).

SQL Server 2008 : Security - Implementing least privilege (part 1) - SQL Server Agent job permissions

A common requirement for SQL Server deployments is for SQL Server Agent jobs to access resources outside of SQL Server. Among other tasks, such jobs are typically used for executing batch files and Integration Services packages.

MySQL for Python : Simple Insertion - Using user-defined variables

Just as in data retrieval, it is inevitable that you will want to utilize user input when inserting data into MySQL. MySQL for Python provides a consistent, Pythonic interface for this.

MySQL for Python : Simple Insertion - Passing an insertion through MySQL for Python

Inserting data into MySQL is a straightforward process that is largely based around ensuring that the database daemon knows where you want your data placed. Inserting data into MySQL may seem a bit more complicated than retrieving it but the previous discussion shows it is still logical, but just requires a few more keywords in order to be useful.

SQL Server : Constraints and Rock Solid Inventory Systems (part 4) - Adding rows out of date order

At the moment, our inventory system robustly handles the insertion of new rows to the end of the inventory (i.e. in date order). However, far more complex is the situation where we need to insert a row when it is not the last in the trail history.