SQL

SQL (Structured Query Language)

Standard programming language for managing and manipulating relational databases.

Relational Database Management Systems (RDBMS)

Systems like MySQL, PostgreSQL, Oracle, and SQL Server.

Database

Organized collection of related data, structured for efficient storage and retrieval.

Table

Collection of rows and columns that store data in a relational format.

INT

Whole numbers without decimal points.

VARCHAR(n)

String with a maximum length of n characters.

DATE

Represents calendar dates.

BOOLEAN

True or False values.

FLOAT / DOUBLE

Decimal numbers with single (FLOAT) or double (DOUBLE) precision.

SELECT

Used to retrieve data from one or more tables.

INSERT

Used to add new rows to a table.

UPDATE

Used to modify existing data in a table.

DELETE

Used to remove rows from a table.

WHERE Clause

Used to filter records based on specified conditions.

ORDER BY

Used to sort the result-set in ascending or descending order.

COUNT()

Counts the number of rows

SUM()

Calculates the sum of values in a column

AVG()

Calculates the average value of a column

MAX()

Finds the maximum value in a column

MIN()

Finds the minimum value in a column

INNER JOIN

Returns only matching records from both tables

LEFT JOIN

Returns all records from the left table and matched records from the right table

RIGHT JOIN

Returns all records from the right table and matched records from the left table

FULL JOIN

Returns all records from both tables

PRIMARY KEY

Uniquely identifies a record in a table

FOREIGN KEY

Establishes a link between two tables using a column that refers to the primary key of another table

UNIQUE

Ensures that all values in a column are unique

NOT NULL

Ensures that a column cannot contain NULL values

Subqueries

Queries nested inside another query.

SQL (Structured Query Language)

SQL is the standard language for interacting with relational databases. It allows users to perform various operations such as querying, updating, and managing data. It is declarative, meaning you specify what you want to achieve, not how to achieve it.

Relational Database Management Systems (RDBMS)

RDBMS are software systems used to manage and maintain relational databases. Popular examples include MySQL, PostgreSQL, Oracle, and SQL Server. They provide a structured way to store, organize, and access data, ensuring data integrity and consistency.

Database

A database is an organized and structured collection of data, stored and accessed electronically. It is designed to efficiently store, manage, and retrieve large amounts of related data, providing a reliable and persistent storage solution.

Table

A table is a fundamental structure in a relational database, consisting of rows and columns. It is used to store data in a structured format, where each row represents a record and each column represents a specific attribute of that record.

INT

INT is a data type used to represent whole numbers, both positive and negative, without any decimal points. It is commonly used for storing integer values such as counts, quantities, or IDs.

VARCHAR(n)

VARCHAR(n) is a data type used to store variable-length character strings, where 'n' specifies the maximum number of characters that can be stored. It is suitable for storing text data such as names, addresses, or descriptions.

DATE

DATE is a data type used to represent calendar dates, typically consisting of year, month, and day. It is commonly used for storing dates of events, records, or transactions.

BOOLEAN

BOOLEAN is a data type used to represent binary values, either True or False. It is commonly used for storing flags or status indicators.

FLOAT / DOUBLE

FLOAT / DOUBLE are data types used to represent decimal numbers with single (FLOAT) or double (DOUBLE) precision. They are commonly used for storing numerical values with fractional parts, such as measurements or financial data.

SELECT

SELECT is a SQL statement used to retrieve data from one or more tables in a database. It allows users to specify the columns to be retrieved and apply conditions to filter the results.

INSERT

INSERT is a SQL statement used to add new rows (records) to a table in a database. It allows users to specify the values to be inserted into each column of the new row.

UPDATE

UPDATE is a SQL statement used to modify existing data in a table. It allows users to change the values of one or more columns in specific rows based on specified conditions.

DELETE

DELETE is a SQL statement used to remove rows (records) from a table in a database. It allows users to delete specific rows based on specified conditions.

WHERE Clause

The WHERE clause is used to filter records based on specified conditions. It is used in SELECT, UPDATE, and DELETE statements to specify which records should be affected by the query.

ORDER BY

ORDER BY is a clause used to sort the result-set of a query in ascending or descending order based on one or more columns. It allows users to arrange the retrieved data in a specific order for better readability or analysis.

COUNT()

COUNT() is an aggregate function that counts the number of rows in a table or the number of non-NULL values in a column. It is commonly used to determine the size of a dataset or the frequency of occurrences.

SUM()

SUM() is an aggregate function that calculates the sum of values in a numeric column. It is commonly used to compute the total value of a set of numbers.

AVG()

AVG() is an aggregate function that calculates the average value of a numeric column. It computes the arithmetic mean of a set of numbers.

MAX()

MAX() is an aggregate function that finds the maximum value in a column. It determines the highest value among a set of values.

MIN()

MIN() is an aggregate function that finds the minimum value in a column. It determines the lowest value among a set of values.

INNER JOIN

INNER JOIN returns only the matching records from both tables involved in the join. It combines rows from two tables based on a related column between them.

LEFT JOIN

LEFT JOIN returns all records from the left table and the matched records from the right table. If there is no match, the result will contain NULL values for the columns from the right table.

RIGHT JOIN

RIGHT JOIN returns all records from the right table and the matched records from the left table. If there is no match, the result will contain NULL values for the columns from the left table.

FULL JOIN

FULL JOIN returns all records from both tables. When there are no matching rows, it fills in NULL values for the missing sides.

PRIMARY KEY

PRIMARY KEY is a column or a set of columns that uniquely identifies each record in a table. It ensures that each row has a unique identifier and helps enforce data integrity.

FOREIGN KEY

FOREIGN KEY establishes a link between two tables by referencing the primary key of another table. It ensures referential integrity between related tables, maintaining consistency of data across the database.

UNIQUE

UNIQUE constraint ensures that all values in a column are unique, preventing duplicate entries. It helps maintain the uniqueness and integrity of data within a column.

NOT NULL

NOT NULL constraint ensures that a column cannot contain NULL values, requiring a value to be present for every record. It prevents missing or incomplete data in a column.

Subqueries

Subqueries are queries nested inside another query. They are used to perform complex data retrieval and filtering operations, allowing users to create dynamic and flexible queries.