What is SQL?

SQL stands for Structured Query Language
SQL lets you access and manipulate databases
SQL became a standard of the American National Standards Institute (ANSI) in 1986, and of the International Organization for Standardization (ISO) in 1987

SQL is Structured Query Language, which is a computer language for storing, manipulating and retrieving data stored in a relational database.

All the Relational Database Management Systems (RDMS) like MySQL, MS Access, Oracle, Sybase, Informix, Postgres and SQL Server use SQL as their standard database language.

A Brief History of SQL

1970 − Dr. Edgar F. "Ted" Codd of IBM is known as the father of relational databases. He described a relational model for databases.
1974 − Structured Query Language appeared.
1978 − IBM worked to develop Codd's ideas and released a product named System/R.
1986 − IBM developed the first prototype of relational database and standardized by ANSI. The first relational database was released by Relational Software which later came to be known as Oracle.

Why SQL is required

SQL is required:

To create new databases, tables and views

To insert records in a database

To update records in a database

To delete records from a database

To retrieve data from a database

What Can SQL do?

SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views

RDBMS

RDBMS stands for Relational Database Management System.

RDBMS is the basis for SQL, and for all modern database systems such as MS SQL Server, IBM DB2, Oracle, MySQL, and Microsoft Access.

The data in RDBMS is stored in database objects called tables. A table is a collection of related data entries and it consists of columns and rows.

Database Tables

A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data.

In this tutorial we will use the well-known Northwind sample database (included in MS Access and MS SQL Server).

CustomerID CustomerName ContactName Address City PostalCode Country

1
Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico

3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico

4
Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK

5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SQL Data Types

Data types are used to represent the nature of the data that can be stored in the database table. For example, in a particular column of a table, if we want to store a string type of data then we will have to declare a string data type of this column.

Data types mainly classified into three categories for every database.

String Data types

Numeric Data types

Date and time Data types

SQL statement

SQL statements are started with any of the SQL commands/keywords like SELECT, INSERT, UPDATE, DELETE, ALTER, DROP etc. and the statement ends with a semicolon (;).

SELECT "column_name" FROM "table_name";

Look at the "Customers" table:

SELECT * FROM Customers;

SQL Commands

These are the some important SQL command:

SELECT: it extracts data from a database.
UPDATE: it updates data in database.
DELETE: it deletes data from database.
CREATE TABLE: it creates a new table.
ALTER TABLE: it is used to modify the table.
DROP TABLE: it deletes a table.
CREATE DATABASE: it creates a new database.
ALTER DATABASE: It is used to modify a database.
INSERT INTO: it inserts new data into a database.
CREATE INDEX: it is used to create an index (search key).
DROP INDEX: it deletes an index.

The SQL AND, OR and NOT Operators

The WHERE clause can be combined with AND, OR, and NOT operators.

The AND and OR operators are used to filter records based on more than one condition:

The AND operator displays a record if all the conditions separated by AND are TRUE.
The OR operator displays a record if any of the conditions separated by OR is TRUE.

The NOT operator displays a record if the condition(s) is NOT TRUE.

AND Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition1 AND condition2 AND condition3 ...;

OR Syntax

SELECT column1, column2, ...
FROM table_name
WHERE condition1 OR condition2 OR condition3 ...;

NOT Syntax

SELECT column1, column2, ...
FROM table_name
WHERE NOT condition;

The SQL SELECT Statement

The SELECT statement is used to select data from a database.

The data returned is stored in a result table, called the result-set.

SELECT Syntax

SELECT column1, column2, ...
FROM table_name;

Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax:

SELECT * FROM table_name;

Demo Database

Below is a selection from the "Customers" table in the Northwind sample database:

CustomerID CustomerName ContactName Address City PostalCode Country

1
Alfreds Futterkiste Maria Anders Obere Str. 57 Berlin 12209 Germany

2 Ana Trujillo Emparedados y helados Ana Trujillo Avda. de la Constitución 2222 México D.F. 05021 Mexico

3 Antonio Moreno Taquería Antonio Moreno Mataderos 2312 México D.F. 05023 Mexico

4
Around the Horn Thomas Hardy 120 Hanover Sq. London WA1 1DP UK

5 Berglunds snabbköp Christina Berglund Berguvsvägen 8 Luleå S-958 22 Sweden

CustomerID	CustomerName	ContactName	Address	City	PostalCode	Country
1	Alfreds Futterkiste	Maria Anders	Obere Str. 57	Berlin	12209	Germany
2	Ana Trujillo Emparedados y helados	Ana Trujillo	Avda. de la Constitución 2222	México D.F.	05021	Mexico
3	Antonio Moreno Taquería	Antonio Moreno	Mataderos 2312	México D.F.	05023	Mexico
4	Around the Horn	Thomas Hardy	120 Hanover Sq.	London	WA1 1DP	UK
5	Berglunds snabbköp	Christina Berglund	Berguvsvägen 8	Luleå	S-958 22	Sweden

SELECT Column Example

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName, City FROM Customers;
Try it Yourself »

SELECT * Example

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

The SQL SELECT DISTINCT Statement

The SELECT DISTINCT statement is used to return only distinct (different) values.

Inside a table, a column often contains many duplicate values; and sometimes you only want to list the different (distinct) values.

SELECT DISTINCT Syntax

SELECT DISTINCT column1, column2, ...
FROM table_name;

SELECT DISTINCT Examples
The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table:

Example
SELECT DISTINCT Country FROM Customers;
Try it Yourself »

The SQL WHERE Clause
The WHERE clause is used to filter records.

The WHERE clause is used to extract only those records that fulfill a specified condition.

WHERE Syntax
SELECT column1, column2, ...
FROM table_name
WHERE condition;

Note: The WHERE clause is not only used in SELECT statement, it is also used in UPDATE, DELETE statement, etc.!

WHERE Clause Example
The following SQL statement selects all the customers from the country "Mexico", in the "Customers" table:

Example
SELECT * FROM Customers
WHERE Country='Mexico';
Try it Yourself »

Text Fields vs. Numeric Fields
SQL requires single quotes around text values (most database systems will also allow double quotes).

However, numeric fields should not be enclosed in quotes:

Example
SELECT * FROM Customers
WHERE CustomerID=1;

Operators in The WHERE Clause
The following operators can be used in the WHERE clause:

OperatorDescriptionExample
=EqualTry it
>Greater thanTry it
<Less thanTry it
>=Greater than or equalTry it
<=Less than or equalTry it
<>Not equal. Note: In some versions of SQL this operator may be written as !=Try it
BETWEENBetween a certain rangeTry it
LIKESearch for a patternTry it
INTo specify multiple possible values for a column
Try it

Difference Between SQL Vs MangoDB?

SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases.

👉 It is used to insert, update, retrieve, and delete data in a database, as well as to create and modify the structure of a database.

📍MongoDB is a non-relational document database that provides support for JSON-like storage.

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ORDERBY Query:

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SQL-OR Operator

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SQL- ROUND()

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SQL-MIN()

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SQL-UPDATE
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SQL-SUM()

SQL-MAX()

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SQL-

Operator	Description	Example
=	Equal	Try it
>	Greater than	Try it
<	Less than	Try it
>=	Greater than or equal	Try it
<=	Less than or equal	Try it
<>	Not equal. Note: In some versions of SQL this operator may be written as !=	Try it
BETWEEN	Between a certain range	Try it
LIKE	Search for a pattern	Try it
IN	To specify multiple possible values for a column	Try it

Pages

SQL Tutorial

A Brief History of SQL

SQL is required: To create new databases, tables and views To insert records in a database To update records in a database To delete records from a database To retrieve data from a database

What Can SQL do?

RDBMS

Database Tables

SQL Data Types

SQL statement

SQL Commands

The SQL AND, OR and NOT Operators

AND Syntax

OR Syntax

NOT Syntax

The SQL SELECT Statement

The SELECT statement is used to select data from a database. The data returned is stored in a result table, called the result-set.

SELECT Syntax

SELECT column1, column2, ...FROM table_name; Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax: SELECT * FROM table_name;

Demo Database

SELECT Column Example

The following SQL statement selects the "CustomerName" and "City" columns from the "Customers" table:

Example

SELECT CustomerName, City FROM Customers; Try it Yourself »

SELECT * Example

The following SQL statement selects all the columns from the "Customers" table:

Example

SELECT * FROM Customers;

The SQL SELECT DISTINCT Statement

SELECT DISTINCT Syntax

SELECT DISTINCT Examples

Example

The SQL WHERE Clause

WHERE Syntax

WHERE Clause Example

Example

Text Fields vs. Numeric Fields

Example

Operators in The WHERE Clause

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SQL is required:

To create new databases, tables and views

To insert records in a database

To update records in a database

To delete records from a database

To retrieve data from a database

The SELECT statement is used to select data from a database.

The data returned is stored in a result table, called the result-set.

SELECT column1, column2, ...
FROM table_name;

Here, column1, column2, ... are the field names of the table you want to select data from. If you want to select all the fields available in the table, use the following syntax:

SELECT * FROM table_name;

SELECT CustomerName, City FROM Customers;
Try it Yourself »