Stairway to T-SQL DML Level 12: Using the MERGE Statement
The final level of this stairway looks at the MERGE statement in detail, focusing on how to perform insert, update and delete logic using the MERGE statement.
The final level of this stairway looks at the MERGE statement in detail, focusing on how to perform insert, update and delete logic using the MERGE statement.
This level of the stairway details the creation of a relational database, as well as filling in some of the history of the relational database model.
The first topic in this stairway will be discussing the TOP clause. The TOP clause allows you to control the number of rows to be returned or affected by a query.
In this level of the Beyond the T-SQL Basics stairway, we will be discussing the different aspects of a subquery.
This level discusses how to use a database VIEW to simplify your Transact-SQL(T-SQL) code. By understanding how to use a VIEW you will be able to better support writing T-SQL code to meet complex business requirements. In this article I will be discussing what a database VIEW is and then providing a number of examples to help you understand how you can use a VIEW to implement different coding scenarios.
There are times when retrieving data for complex business requirement requires you to temporarily store one or more results sets for a short period of time. Typically these temporary tables are stored in the scope of the current connection, but they may also need to be available across multiple connections.
There are times where you need to write a single T-SQL statement that is able to return different T-SQL expressions based on the evaluation of another expression. When you need this kind of functionality you can use the CASE expression or IIF function to meet this requirement. In this Stairway level Gregory Larsen reviews the CASE and IIF syntax and showing you examples of how the CASE expression and IIF function.
No one wants to use more keystrokes than they have to when they write a chunk of T-SQL code. To help with minimizing the number of characters a T-SQL developer needs to type the Microsoft team introduced three new shortcuts operators when they release SQL Server 2008. These shorts cuts are the String Concatenation, Add EQUALS, and the Subtract EQUALS operators.
There times when you need to write T-SQL code that creates specific T-SQL Code and executes it. When you do this you are creating dynamic T-SQL code. When writing dynamic T-SQL you need to understand how dynamic code opens the possibilities for a SQL injection attack.
In this level, Rob Sheldon explains what XML is, and describes the components of an XML document, Elements and Attributes. He explains the basics of tags, entity references, enclosed text, comments and declarations
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I set up a few users on my SQL Server 2022 instance.
CREATE LOGIN User1 WITH PASSWORD = 'Demo12#1' CREATE USER User1 FOR LOGIN User1 GO CREATE LOGIN User2 WITH PASSWORD = 'Demo12#2' CREATE USER User2 FOR LOGIN User2 GO CREATE LOGIN User3 WITH PASSWORD = 'Demo12#3' CREATE USER User3 FOR LOGIN User3 GOI then created a schema that one of them owned. Under this schema, I added a table with some data.
CREATE SCHEMA MySchema AUTHORIZATION User1
GO
CREATE TABLE Myschema.MyTable(myid INT)
GO
INSERT MySchema.MyTable
(
myid
)
VALUES
(1), (2), (3)
GO
SELECT * FROM MySchema.MyTable
GO
I granted rights and verified that User2 could access this table.
GRANT SELECT ON Myschema.MyTable TO User2 GO SETUSER 'USER2' GO SELECT * FROM MySchema.MyTable GOThis worked. Now, I move this schema to a new user.
ALTER AUTHORIZATION ON SCHEMA::Myschema TO User3; GOWhat happens with this code?
SETUSER 'USER2' GO SELECT * FROM MySchema.MyTable GOSee possible answers