SQL Data Definition Language - RamNayakTech/knowledge-hub GitHub Wiki

Here are the key topics related to SQL DDL:

1. CREATE

CREATE TABLE: Used to create a new table in the database.

CREATE TABLE table_name (
    column1 datatype PRIMARY KEY,
    column2 datatype,
    column3 datatype
);

CREATE DATABASE: Creates a new database.
```
CREATE DATABASE database_name;
```

CREATE INDEX: Creates an index on a table.

CREATE INDEX index_name
ON table_name (column_name);

CREATE VIEW: Creates a virtual table (view) based on the result set of a SELECT query.
```
CREATE VIEW view_name AS
SELECT column1, column2
FROM table_name
WHERE condition;
```

2. ALTER

ALTER TABLE: Used to modify an existing table's structure.

Add a new column:

ALTER TABLE table_name
ADD column_name datatype;

Modify an existing column:

ALTER TABLE table_name
MODIFY COLUMN column_name datatype;

Drop a column:

ALTER TABLE table_name
DROP COLUMN column_name;

3. DROP

DROP TABLE: Deletes an existing table and its data.
```
DROP TABLE table_name;
```
DROP DATABASE: Deletes an entire database and its data.
```
DROP DATABASE database_name;
```
DROP INDEX: Deletes an index.
```
DROP INDEX index_name ON table_name;
```
DROP VIEW: Deletes a view.
```
DROP VIEW view_name;
```

4. TRUNCATE

TRUNCATE TABLE: Removes all rows from a table without logging individual row deletions. It's faster than the DELETE statement for large tables.
```
TRUNCATE TABLE table_name;
```

5. RENAME

RENAME TABLE: Changes the name of a table.

RENAME TABLE old_table_name TO new_table_name;

Example:

Here's a combined example of creating, altering, and dropping a table:

-- Create a table
CREATE TABLE Employees (
    EmployeeID INT PRIMARY KEY,
    FirstName VARCHAR(50),
    LastName VARCHAR(50),
    DepartmentID INT
);

-- Alter the table to add a new column
ALTER TABLE Employees
ADD DateOfBirth DATE;

-- Drop the table
DROP TABLE Employees;