SQL AUTO_INCREMENT: auto-increment sequence

The AUTO_INCREMENT attribute in SQL is used to automatically generate a unique number whenever a new record is inserted into a table. This is often used with primary key column of the table.

MySQL:

In MySQL, you use the AUTO_INCREMENT keyword to perform this task.

Here's an example of creating a table with an AUTO_INCREMENT primary key:

CREATE TABLE Employees (
    ID int NOT NULL AUTO_INCREMENT,
    FirstName varchar(255) NOT NULL,
    LastName varchar(255),
    PRIMARY KEY (ID)
);

In this example, the ID field is set to auto-increment. This means that every time you insert a new record into the Employees table, you do not have to specify a value for the ID field. MySQL will automatically add a unique value.

PostgreSQL:

In PostgreSQL, the SERIAL keyword is used to perform auto-increment.

CREATE TABLE Employees (
    ID SERIAL PRIMARY KEY,
    FirstName varchar(255) NOT NULL,
    LastName varchar(255)
);

SQL Server:

In SQL Server, you use the IDENTITY property to create an auto-increment field.

CREATE TABLE Employees (
    ID int IDENTITY(1,1) PRIMARY KEY,
    FirstName varchar(255) NOT NULL,
    LastName varchar(255)
);

In this SQL Server example, IDENTITY(1,1) is used to create an auto-incrementing field. The two parameters specify the seed (starting value) and increment, respectively. So IDENTITY(1,1) means start at 1 and increment by 1 for each new record.

Please note that in all these examples, you do not need to specify a value for the ID field when inserting new records. The DBMS automatically assigns a new, unique value to the field.

Creating auto-increment columns in SQL: Define a column with AUTO_INCREMENT to automatically generate unique values.
```
CREATE TABLE TableName (
    ID INT AUTO_INCREMENT,
    Name VARCHAR(255),
    PRIMARY KEY (ID)
);
```
AUTO_INCREMENT in primary key definition: Use AUTO_INCREMENT when defining a primary key for automatic value generation.
```
CREATE TABLE TableName (
    ID INT PRIMARY KEY AUTO_INCREMENT,
    Name VARCHAR(255)
);
```

Setting starting value for AUTO_INCREMENT: Specify a starting value for the AUTO_INCREMENT sequence.

CREATE TABLE TableName (
    ID INT AUTO_INCREMENT,
    Name VARCHAR(255),
    PRIMARY KEY (ID)
) AUTO_INCREMENT = 1001;

Restarting AUTO_INCREMENT sequence in SQL: Restart the AUTO_INCREMENT sequence to a specific value.
```
ALTER TABLE TableName
AUTO_INCREMENT = 1;
```
Removing AUTO_INCREMENT property in SQL: Remove the AUTO_INCREMENT property from a column.
```
ALTER TABLE TableName
MODIFY COLUMN ID INT;
```

Using AUTO_INCREMENT with composite keys: Incorporate AUTO_INCREMENT into a composite primary key.

CREATE TABLE TableName (
    ID INT AUTO_INCREMENT,
    OtherID INT,
    Name VARCHAR(255),
    PRIMARY KEY (ID, OtherID)
);

Retrieving last inserted ID with AUTO_INCREMENT: Retrieve the last inserted ID after an INSERT operation.
- Syntax may vary based on the database engine.
```
SELECT LAST_INSERT_ID();
```