DBMS & SQL · Module 3 of 10

Creating tables: DDL

Define structure with CREATE, ALTER and DROP.

📖 Key ideas

DDL (Data Definition Language) defines structure.
CREATE TABLE students (id INT PRIMARY KEY, name VARCHAR(50));
ALTER TABLE adds or changes columns.
DROP TABLE deletes the whole table; TRUNCATE removes all rows but keeps the table.
Data types: INT, VARCHAR(n), DATE, DECIMAL(p,s), BOOLEAN.

💡 Real-life example: DDL is the architect's plan: rooms (tables) and their sizes (columns) are designed before people move in.

CREATE TABLEMakes a new table

ALTER TABLEChanges a table structure

DROP TABLEDeletes a table completely

VARCHAR(n)Text up to n characters