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Topics

Introduction to SQL

What is SQL?SQL HistorySQL StandardsSQL vs NoSQLSQL Database Management Systems

SQL Basics

SQL SyntaxSQL CommentsSQL Data TypesSQL OperatorsSQL ExpressionsSQL LiteralsSQL IdentifiersSQL KeywordsSQL Case Sensitivity

SQL Database Fundamentals

Database ConceptsTables and FieldsPrimary KeysForeign KeysIndexesConstraintsNormalizationDenormalizationSQL Schema Design

SQL Data Manipulation

SQL SELECT StatementSQL INSERT StatementSQL UPDATE StatementSQL DELETE StatementSQL MERGE StatementSQL AliasesSQL WildcardsSQL LIKE OperatorSQL IN OperatorSQL BETWEEN OperatorSQL NULL ValuesSQL ORDER BY ClauseSQL LIMIT ClauseSQL OFFSET Clause

SQL Filtering and Sorting

SQL WHERE ClauseSQL AND, OR, NOT OperatorsSQL GROUP BY ClauseSQL HAVING ClauseSQL DISTINCT KeywordSQL TOP Clause

SQL Joins

SQL INNER JOINSQL LEFT JOINSQL RIGHT JOINSQL FULL OUTER JOINSQL CROSS JOINSQL Self JOINSQL Natural JOINSQL Multiple JOINs

SQL Functions

SQL Aggregate FunctionsSQL Scalar FunctionsSQL String FunctionsSQL Numeric FunctionsSQL Date FunctionsSQL Conversion FunctionsSQL System FunctionsSQL User-Defined Functions

SQL Subqueries

SQL Subquery BasicsCorrelated SubqueriesNested SubqueriesSQL EXISTS OperatorSQL ANY and ALL OperatorsSubqueries in SELECTSubqueries in FROMSubqueries in WHERE

SQL Views

Creating SQL ViewsAltering SQL ViewsDropping SQL ViewsUpdatable ViewsMaterialized ViewsView Limitations

SQL Transactions

SQL Transaction BasicsACID PropertiesBEGIN TRANSACTIONCOMMITROLLBACKSAVEPOINTTransaction Isolation Levels

SQL Data Definition

SQL CREATE TABLESQL ALTER TABLESQL DROP TABLESQL TRUNCATE TABLESQL CREATE INDEXSQL DROP INDEXSQL CREATE DATABASESQL ALTER DATABASESQL DROP DATABASE

SQL Data Control

SQL GRANTSQL REVOKESQL RolesSQL UsersSQL Privileges

SQL Performance Optimization

SQL Query OptimizationSQL Execution PlansSQL Index OptimizationSQL Query TuningSQL CachingSQL Partitioning

Advanced SQL Concepts

SQL Stored ProceduresSQL TriggersSQL CursorsSQL Common Table ExpressionsSQL Window FunctionsSQL Pivot and UnpivotSQL JSON OperationsSQL XML OperationsSQL Full-Text Search

SQL Best Practices

SQL Naming ConventionsSQL Code OrganizationSQL Error HandlingSQL Security Best PracticesSQL Backup and RecoverySQL Version Control

SQL CREATE TABLE Statement

The CREATE TABLE statement is a fundamental SQL command used to create new tables in a database. It defines the structure of a table, including its columns, data types, and constraints.

Basic Syntax

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

CREATE TABLE table_name (
    column1 datatype constraint,
    column2 datatype constraint,
    column3 datatype constraint,
    ...
);

Key Components

  • table_name: The name you want to give to your new table.
  • column1, column2, etc.: The names of the columns in your table.
  • datatype: The SQL data type for each column (e.g., INT, VARCHAR, DATE).
  • constraint: Optional rules for the data in each column (e.g., NOT NULL, UNIQUE).

Example: Creating a Simple Table

Let's create a basic "employees" table:

CREATE TABLE employees (
    employee_id INT PRIMARY KEY,
    first_name VARCHAR(50) NOT NULL,
    last_name VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE,
    hire_date DATE
);

This example demonstrates the creation of a table with various column types and constraints.

Adding Constraints

Constraints are rules enforced on the data columns in a table. They are crucial for maintaining data integrity. Common constraints include:

  • PRIMARY KEY: Uniquely identifies each record in the table.
  • FOREIGN KEY: Establishes a link between two tables.
  • NOT NULL: Ensures a column cannot have a NULL value.
  • UNIQUE: Ensures all values in a column are different.
  • CHECK: Ensures all values in a column satisfy a specific condition.

Example: Table with Constraints

Here's an example of a "orders" table with various constraints:

CREATE TABLE orders (
    order_id INT PRIMARY KEY,
    customer_id INT NOT NULL,
    order_date DATE DEFAULT CURRENT_DATE,
    total_amount DECIMAL(10, 2) CHECK (total_amount > 0),
    FOREIGN KEY (customer_id) REFERENCES customers(customer_id)
);

Best Practices

  • Use meaningful and consistent naming conventions for tables and columns.
  • Choose appropriate data types to optimize storage and performance.
  • Implement primary keys for each table to ensure data integrity.
  • Use foreign keys to establish relationships between tables.
  • Apply constraints to enforce business rules and data consistency.
  • Consider normalization principles to reduce data redundancy.

Considerations

When creating tables, keep these points in mind:

  • Table and column names are typically case-insensitive, but this can vary by database system.
  • Some databases have limits on the number of columns per table.
  • Consider future scalability when designing your table structure.
  • Be cautious when using AUTO_INCREMENT or IDENTITY for primary keys in distributed systems.

Understanding the CREATE TABLE statement is crucial for effective SQL schema design. It forms the foundation of your database structure and plays a vital role in overall database performance and maintainability.