SQL: INSERT, UPDATE, DELETE, and CREATE TABLE

Beyond querying data with SELECT, SQL provides statements to modify data and define table structures. These are part of the Data Manipulation Language (DML) and Data Definition Language (DDL).

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Data Definition Language (DDL) — CREATE TABLE

DDL statements define the structure of the database. The most important DDL statement at A-Level is CREATE TABLE.

Basic Syntax

CREATE TABLE TableName (
    Column1 DataType CONSTRAINT,
    Column2 DataType CONSTRAINT,
    ...
    PRIMARY KEY (Column1)
);

Example

CREATE TABLE Students (
    StudentID INTEGER PRIMARY KEY,
    FirstName VARCHAR(50) NOT NULL,
    Surname VARCHAR(50) NOT NULL,
    DateOfBirth DATE,
    Email VARCHAR(100) UNIQUE,
    FormGroup VARCHAR(5)
);

Common Data Types

Data Type	Description
INTEGER / INT	Whole numbers
VARCHAR(n)	Variable-length text up to n characters
CHAR(n)	Fixed-length text of exactly n characters
DATE	Date value (YYYY-MM-DD)
FLOAT / REAL	Decimal numbers
BOOLEAN	TRUE or FALSE
TEXT	Large text blocks

Common Constraints