SQL Seeker

Schema Management

SQL CREATE TABLE

Creating Tables with CREATE TABLE

CREATE TABLE defines tables with column constraints like PRIMARY KEY.

Introduction to SQL CREATE TABLE

The CREATE TABLE statement in SQL is used to create a new table in a database. It defines the structure of the table by specifying the columns, their data types, and optional constraints such as primary keys.

Basic Syntax of CREATE TABLE

The basic syntax for creating a table in SQL is as follows:

Understanding Data Types

Each column in a SQL table must be assigned a data type. Common data types include INT for integers, VARCHAR(n) for variable-length strings, DATE for date values, and BOOLEAN for true/false values.

Adding Constraints to Columns

Constraints are used to limit the type of data that can go into a table. They ensure the accuracy and reliability of the data. Here are some common constraints:

  • PRIMARY KEY: Uniquely identifies each row in a table.
  • FOREIGN KEY: Ensures referential integrity between two tables.
  • NOT NULL: Ensures that a column cannot have a NULL value.
  • UNIQUE: Ensures all values in a column are different.
  • CHECK: Ensures that all values in a column satisfy a specific condition.

Example: Creating a Table with Constraints

Let's create a simple table named Employees with various constraints:

Conclusion

Using the CREATE TABLE statement, you can define the structure of your database tables with precision. By applying constraints, you ensure data integrity and consistency. Understanding how to effectively use this command is fundamental for database design and management.

Schema Management

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ALTER TABLE