Hello Dev, welcome to our journal article about all objects in SQL Server. As you know, SQL Server is a popular relational database management system used by many businesses and organizations around the world. In this article, we will discuss the different objects that you can create and manage in SQL Server. By the end of this article, you will have a better understanding of how to use these objects effectively in your own projects.
What are Objects in SQL Server?
In SQL Server, objects are defined as any entity that you can create or manage within the database. These objects can be used to store data, manage security, define business rules, and more. There are many different types of objects to choose from, depending on your specific needs. In the following sections, we will go over each type of object in more detail.
Tables
Tables are the most common type of object in SQL Server. They are used to store data in a structured manner, allowing you to easily retrieve, update, and delete records. Tables can be created using the CREATE TABLE statement, and can be modified using various other statements such as ALTER TABLE and DROP TABLE.
When creating a table, you must specify the columns that the table will have, as well as their data types and any constraints or rules that should be applied. Tables can also have indexes defined on them, which can help speed up queries that retrieve data from the table.
Here is an example of creating a simple table:
Column Name |
Data Type |
Constraints |
|---|---|---|
id |
INT |
PRIMARY KEY |
name |
VARCHAR(50) |
NOT NULL |
age |
INT |
|
email |
VARCHAR(100) |
UNIQUE |
In this example, we have created a table with four columns: id, name, age, and email. The id column is the primary key of the table, which means that it uniquely identifies each record in the table. The name column is a variable-length character field with a maximum length of 50 characters, and it is not allowed to be NULL. The age column is an integer field that does not have any constraints applied to it. The email column is also a variable-length character field, but in this case it is set to be unique, meaning that no two records can have the same email address.
Tables can be queried using the SELECT statement, which allows you to retrieve data from one or more tables at a time. You can also use the INSERT statement to add new records to a table, the UPDATE statement to modify existing records, and the DELETE statement to remove records from a table.
FAQ
What is a primary key?
A primary key is a column or combination of columns that uniquely identifies each record in a table. It is used to enforce the integrity of the data in the table, and to ensure that each record can be accessed and modified as needed.
What are data types?
Data types are used to define the type of data that can be stored in a column of a table. Examples of data types include INT (integer), VARCHAR (variable-length character), and DATE (date and time).
What are constraints?
Constraints are used to enforce rules or restrictions on the data that can be stored in a column of a table. Examples of constraints include PRIMARY KEY, NOT NULL, and UNIQUE.
What are indexes?
Indexes are used to speed up queries that retrieve data from a table. They work by creating a separate data structure that allows for faster access to the data in the table.
Views
Views are virtual tables that are defined by a query. They allow you to simplify complex queries by creating a view that retrieves the data you need from one or more tables. Views can also be used to limit the amount of data that users are able to access, by only allowing them to see certain columns or rows of data.
Views can be created using the CREATE VIEW statement, and can be modified using the ALTER VIEW statement. Here is an example of creating a simple view:
CREATE VIEW myView
AS
SELECT name, age
FROM myTable
WHERE age > 18;
In this example, we have created a view called myView, which retrieves the name and age columns from the myTable table, but only includes records where the age is greater than 18. This view can then be queried just like a regular table.
FAQ
What is a query?
A query is a request for data from a database. Queries are typically written in SQL (Structured Query Language), which is a programming language used to manage and manipulate data in a database.
What is a virtual table?
A virtual table is a table that is not actually stored in the database, but is instead created dynamically based on a query. Views are an example of a virtual table.
What is data access control?
Data access control is the process of limiting the amount of data that users are able to access in a database, based on their role or level of authorization. Views can be used to implement data access control, by only allowing users to see certain columns or rows of data.
Stored Procedures
Stored procedures are precompiled SQL statements that are stored in the database. They are used to perform common tasks or operations, such as inserting or updating data, without having to write the same code over and over again. Stored procedures can also be used to enforce business rules or apply complex calculations to data.
Stored procedures can be created using the CREATE PROCEDURE statement, and can be modified using the ALTER PROCEDURE statement. Here is an example of creating a simple stored procedure:
CREATE PROCEDURE myProc
@name VARCHAR(50),
@age INT,
@email VARCHAR(100)
AS
BEGIN
INSERT INTO myTable (name, age, email) VALUES (@name, @age, @email)
END;
In this example, we have created a stored procedure called myProc, which takes three parameters: name, age, and email. These parameters are then used to insert a new record into the myTable table. This stored procedure can then be called from within other SQL statements or from application code.
FAQ
What is precompiled SQL?
Precompiled SQL is SQL code that has been compiled into an executable format, rather than being interpreted at runtime. This can improve the performance of SQL code by reducing the amount of time it takes to execute.
What are parameters?
Parameters are values that are passed into a stored procedure, function, or query. They allow you to reuse the same code with different values, without having to rewrite the code each time.
What is application code?
Application code is the code that makes up an application or program, such as a web application or desktop application. Application code can interact with a SQL Server database using SQL statements, stored procedures, or other methods.
Functions
Functions are similar to stored procedures, but they return a value rather than performing an action. They can be used to perform calculations, string manipulation, or other operations on data within the database.
Functions can be created using the CREATE FUNCTION statement, and can be modified using the ALTER FUNCTION statement. Here is an example of creating a simple function:
CREATE FUNCTION myFunc
(@num1 INT, @num2 INT)
RETURNS INT
AS
BEGIN
RETURN @num1 + @num2
END;
In this example, we have created a function called myFunc, which takes two parameters: num1 and num2. This function then returns the sum of these two values. This function can then be used in other SQL statements, just like any other function.
FAQ
What is string manipulation?
String manipulation is the process of modifying or manipulating text strings in order to achieve a desired result. Examples of string manipulation include trimming whitespace, converting text between uppercase and lowercase, and removing certain characters from a string.
What is a return value?
A return value is the value that a function or stored procedure returns when it is executed. This value can be used in other SQL statements or application code to perform further operations on the data.
What are calculations?
Calculations are operations performed on data that result in a new value. Examples of calculations include addition, subtraction, multiplication, and division.
Triggers
Triggers are special types of stored procedures that are automatically executed when certain events occur in the database. For example, a trigger can be set up to automatically update a certain column in a table when a record is inserted or updated, or to send an email notification when a certain condition is met.
Triggers can be created using the CREATE TRIGGER statement, and can be modified using the ALTER TRIGGER statement. Here is an example of creating a simple trigger:
CREATE TRIGGER myTrigger
ON myTable
AFTER INSERT, UPDATE
AS
BEGIN
UPDATE myTable SET dateModified = GETDATE() WHERE id = (SELECT id FROM inserted)
END;
In this example, we have created a trigger called myTrigger, which is executed after an insert or update operation is performed on the myTable table. This trigger then sets the dateModified column of the affected record to the current date and time. Triggers can be very useful for enforcing business rules or performing complex actions based on events within the database.
FAQ
What are events?
Events are actions or changes that occur within the database, such as inserting, updating, or deleting records. Triggers can be set up to automatically respond to these events by performing certain actions or calculations.
What is GETDATE()?
GETDATE() is a function in SQL Server that returns the current date and time. It is often used in triggers or stored procedures to record the date and time that a certain action occurred.
What is a business rule?
A business rule is a rule or policy that is defined by a business or organization, and is often enforced through software or database systems. Examples of business rules include requiring a certain level of authorization to access certain data, or ensuring that certain fields in a form are filled out before it can be submitted.
Indexes
Indexes are used to speed up queries that retrieve data from a table. They work by creating a separate data structure that allows for faster access to the data in the table.
Indexes can be created using the CREATE INDEX statement, and can be modified using the ALTER INDEX statement. Here is an example of creating a simple index:
CREATE INDEX myIndex ON myTable (name);
In this example, we have created an index called myIndex on the name column of the myTable table. This index can then be used to speed up queries that retrieve data from the table based on the name column.
FAQ
What is a data structure?
A data structure is a way of organizing data so that it can be accessed and manipulated efficiently. Examples of data structures in SQL Server include tables, indexes, and views.
What is a query optimizer?
A query optimizer is a component of SQL Server that analyzes SQL statements and determines the most efficient way to retrieve the requested data. This process can involve choosing the best indexes to use, optimizing join operations, and other performance enhancements.
What are join operations?
Join operations are used to combine data from two or more tables into a single result set. Join operations can be performed using various types of joins, such as inner joins, outer joins, and cross joins.
Constraints
Constraints are used to enforce rules or restrictions on the data that can be stored in a column of a table. Examples of constraints include PRIMARY KEY, FOREIGN KEY, UNIQUE, and CHECK constraints.
Constraints can be added to a table using the ALTER TABLE statement, and can be modified or removed using the same statement. Here is an example of creating a simple constraint:
ALTER TABLE myTable
ADD CONSTRAINT myConstraint UNIQUE (email);
In this example, we have added a UNIQUE constraint called myConstraint to the email column of the myTable table. This constraint ensures that no two records in the table can have the same email address.
FAQ
What is a primary key?
A primary key is a column or combination of columns that uniquely identifies each record in a table. It is used to enforce the integrity of the data in the table, and to ensure that each record can be accessed and modified as needed.
What is a foreign key?
A foreign key is a column or combination of columns that refers to the primary key of another table. It is used to establish a relationship between two tables, and to ensure that the data in the tables remains consistent.
What is a check constraint?
A check constraint is a constraint that specifies a condition that must be true for data to be added or updated in a column of a table. For example, you could add a check constraint to a date column that ensures that dates are entered in a certain format.
Transactions
Transactions are used to group multiple SQL statements together into a single atomic operation. This means that either all of the statements in the transaction are executed successfully, or none of them are executed at all.
Transactions can be started using the BEGIN TRANSACTION statement, and can be committed using the COMMIT TRANSACTION statement or rolled back using the ROLLBACK TRANSACTION statement. Here is an example of using transactions:
BEGIN TRANSACTION
UPDATE myTable SET name = ‘John’ WHERE id = 1
UPDATE myTable SET age = 30 WHERE id = 1
COMMIT TRANSACTION
In this example, we have started a new transaction, then updated two columns of the record with id 1 in the myTable table. If both of these statements are executed successfully, the transaction is then committed, which means that the changes are permanently saved to the database. If either of the statements fails, the transaction is rolled back, which means that no changes are made to the database.
FAQ
What is an atomic operation?
An atomic operation is an operation that is indivisible and irreducible. In the context of SQL Server, it means that either all of the statements in a transaction are executed successfully, or none of them are executed at all.
What is a commit?
A commit is a command that saves the changes made in a transaction to the database. Once a transaction is committed, the changes made in the transaction are permanent and cannot be undone.
What is a rollback?
A rollback is a command that undoes the changes made in a transaction, effectively restoring the database to its original state before the transaction began. Rollbacks are typically used when a transaction encounters an error or other problem that prevents it from completing successfully.
Security
SQL Server includes a variety of security features that can be used to protect your data and ensure that only authorized users are able to access it. These features include authentication, encryption, and authorization.
Authentication is the process of verifying the identity of a user or application, typically through the use of a username and password. SQL Server supports various authentication modes, including Windows Authentication and SQL Server Authentication.
Encryption is the process of converting data into a format that can only be read by authorized users. SQL Server supports various encryption algorithms, including symmetric key encryption and asymmetric key encryption.
Authorization is the process of determining which users or applications are allowed to access which data. SQL Server includes various authorization features, including user and role permissions, schema permissions, and object permissions.
FAQ
What is authentication?
Authentication is the process of verifying the identity of a