List of SQL Statements from CodeAcedemy

SQL, ‘Structured Query Language’, is a programming language designed to manage data stored in relational databases. SQL operates through simple, declarative statements. This keeps data accurate and secure, and helps maintain the integrity of databases, regardless of size.

Here’s an appendix of commonly used commands.



ALTER TABLE table_name ADD column datatype;

ALTER TABLE lets you add columns to a table in a database.


SELECT column_name(s)
FROM table_name
WHERE column_1 = value_1
AND column_2 = value_2;

AND is an operator that combines two conditions. Both conditions must be true for the row to be included in the result set.


SELECT column_name AS 'Alias'
FROM table_name;

AS is a keyword in SQL that allows you to rename a column or table using an alias.


SELECT AVG(column_name)
FROM table_name;

AVG() is an aggregate function that returns the average value for a numeric column.


SELECT column_name(s)
FROM table_name
WHERE column_name BETWEEN value_1 AND value_2;

The BETWEEN operator is used to filter the result set within a certain range. The values can be numbers, text or dates.


SELECT COUNT(column_name)
FROM table_name;

COUNT() is a function that takes the name of a column as an argument and counts the number of rows where the column is not NULL.


CREATE TABLE table_name (column_1 datatype, column_2 datatype, column_3 datatype);

CREATE TABLE creates a new table in the database. It allows you to specify the name of the table and the name of each column in the table.


DELETE FROM table_name WHERE some_column = some_value;

DELETE statements are used to remove rows from a table.


FROM table_name
GROUP BY column_name;

GROUP BY is a clause in SQL that is only used with aggregate functions. It is used in collaboration with the SELECT statement to arrange identical data into groups.


SELECT column_name(s) FROM table_1
JOIN table_2
ON table_1.column_name = table_2.column_name;

An inner join will combine rows from different tables if the join condition is true.


INSERT INTO table_name (column_1, column_2, column_3) VALUES (value_1, 'value_2', value_3);

INSERT statements are used to add a new row to a table.


SELECT column_name(s)
FROM table_name
WHERE column_name LIKE pattern;

LIKE is a special operator used with the WHERE clause to search for a specific pattern in a column.


SELECT column_name(s)
FROM table_name
LIMIT number;

LIMIT is a clause that lets you specify the maximum number of rows the result set will have.


SELECT MAX(column_name)
FROM table_name;

MAX() is a function that takes the name of a column as an argument and returns the largest value in that column.


SELECT MIN(column_name)
FROM table_name;

MIN() is a function that takes the name of a column as an argument and returns the smallest value in that column.


SELECT column_name
FROM table_name
WHERE column_name = value_1
OR column_name = value_2;

OR is an operator that filters the result set to only include rows where either condition is true.


SELECT column_name
FROM table_name
ORDER BY column_name ASC|DESC;

ORDER BY is a clause that indicates you want to sort the result set by a particular column either alphabetically or numerically.


SELECT column_name(s) FROM table_1
LEFT JOIN table_2
ON table_1.column_name = table_2.column_name;

An outer join will combine rows from different tables even if the the join condition is not met. Every row in the left table is returned in the result set, and if the join condition is not met, then NULL values are used to fill in the columns from the righttable.


SELECT ROUND(column_name, integer)
FROM table_name;

ROUND() is a function that takes a column name and an integer as an argument. It rounds the values in the column to the number of decimal places specified by the integer.


SELECT column_name FROM table_name;

SELECT statements are used to fetch data from a database. Every query will begin with SELECT.


SELECT DISTINCT column_name FROM table_name;

SELECT DISTINCT specifies that the statement is going to be a query that returns unique values in the specified column(s).


SELECT SUM(column_name)
FROM table_name;

SUM() is a function that takes the name of a column as an argument and returns the sum of all the values in that column.


UPDATE table_name
SET some_column = some_value
WHERE some_column = some_value;

UPDATE statments allow you to edit rows in a table.


SELECT column_name(s)
FROM table_name
WHERE column_name operator value;

WHERE is a clause that indicates you want to filter the result set to include only rows where the following condition is true.

Background to Relational Database Management Systems (RDBMS)

Relational Database Management Systems (RDBMS)

A relational database management system (RDBMS) is a program that lets you create, update, and administer a relational database. Most relational database management systems use SQL to access the database.

There are more similarities than differences between the different RDBMS, but the SQL syntax may be slightly different depending on which RDBMS you are using.

Here is a brief description of popular types of RDBMS


SQLite is a popular open source SQL database. It is able to store an entire database in a single file. One of the biggest advantages this provides is that all of the data can be stored locally without having to connect your database to a server.

SQLite is a popular choice for databases in cellphones, PDAs, MP3 players, set-top boxes, and other electronic gadgets. The SQL course on Codecademy also uses SQLite.


MySQL is the most popular open source SQL database. It is typically used for web application development, and often accessed using PHP.

The main advantages of MySQL are that it is easy to use, inexpensive, reliable (has been around since 1995) and has a large community of developers who can help answer questions.

Some of the disadvantages are that it has been known to suffer from poor performance when scaling, open source development has lagged since Oracle has taken control of MySQL, and it does not include some advanced features that developers may be used to.


PostgreSQL is an open source SQL database that is not controlled by any corporation. It is typically used for web application development.

PostgreSQL shares many of the same advantages of MySQL. It is easy to use, inexpensive, reliable, and has a large community of developers. It also provides some additional features such as foreign key support without requiring complex configuration.

The main disadvantage of PostgreSQL is that it is slower in performance than other databases such as MySQL. It is also less popular than MySQL which makes it harder to come by hosts or service providers that offer managed PostgreSQL instances.

Oracle DB

Oracle DB is owned by the Oracle corporation and the code is not open sourced.

Oracle is used for large applications, particularly in the banking industry. Most of the world’s top banks run Oracle applications because Oracle offers a powerful combination of technology and comprehensive, pre-integrated business applications, including key functionality built specifically for banks.

The main disadvantage of using Oracle is that it is not free to use like its open source competitors and can be quite expensive.

SQL Server

SQL Server is owned by Microsoft. Like Oracle DB, the code is also close sourced.

SQL Server is mainly used by large enterprise applications. The major difference between Oracle and SQL Server is that SQL Server only supports the Windows Operating System.

Microsoft offers a free entry level version called Express, but can become very expensive as you scale your application.

How to backup (export) MySQL database using HeidiSQL

do not use more than one "!" in post titles.

in heidisql:
right click on database in tree on the left.
select "Export database as SQL"
in the dialog, on the right select
Database(s) [x] Create box
Table(s) [x] Create box
Data: select INSERT
Output: select One big file
FileName: click on small disk symbol at right edge to select the name and location (path) where output file is to be stored
click "Export" button (lower right)

transfer output file to new PC
start heidisql
select from Menu "Tools" / "Load SQL file…"
in open dialog, select the transferred .sql file
after file has loadled into the upper pane, press F9

that should be it.

By vichhaiy Posted in DB, WEP


MariaDB – Drop-in replacement for Oracle MySQL server

MariaDB is a community-developed fork of the MySQL server. MariaDB is going to be default in many popular Linux distro and open source project. Red Hat will switch the default database in its enterprise distribution, RHEL (including its clones such as CentOS), from MySQL to MariaDB, when version 7 is released in 2014. I started testing MariaDB and found no problems at all. The speed is same or better in some cases.

Operating system : Cross-platform
Purpose : RDBMS
Targets : DevOps/Sysadmins
License : GPL/LGPL
Download url :

SQL vs NoSQL Database Differences Explained with few Example DB

SQL vs NoSQL: High-Level Differences

  • SQL databases are primarily called as Relational Databases (RDBMS); whereas NoSQL database are primarily called as non-relational or distributed database.
  • SQL databases are table based databases whereas NoSQL databases are document based, key-value pairs, graph databases or wide-column stores. This means that SQL databases represent data in form of tables which consists of n number of rows of data whereas NoSQL databases are the collection of key-value pair, documents, graph databases or wide-column stores which do not have standard schema definitions which it needs to adhered to.
  • SQL databases have predefined schema whereas NoSQL databases have dynamic schema for unstructured data.
  • SQL databases are vertically scalable whereas the NoSQL databases are horizontally scalable. SQL databases are scaled by increasing the horse-power of the hardware. NoSQL databases are scaled by increasing the databases servers in the pool of resources to reduce the load.
  • SQL databases uses SQL ( structured query language ) for defining and manipulating the data, which is very powerful. In NoSQL database, queries are focused on collection of documents. Sometimes it is also called as UnQL (Unstructured Query Language). The syntax of using UnQL varies from database to database.
  • SQL database examples: MySql, Oracle, Sqlite, Postgres and MS-SQL. NoSQL database examples: MongoDB, BigTable, Redis, RavenDb, Cassandra, Hbase, Neo4j and CouchDb
  • For complex queries: SQL databases are good fit for the complex query intensive environment whereas NoSQL databases are not good fit for complex queries. On a high-level, NoSQL don’t have standard interfaces to perform complex queries, and the queries themselves in NoSQL are not as powerful as SQL query language.
  • For the type of data to be stored: SQL databases are not best fit for hierarchical data storage. But, NoSQL database fits better for the hierarchical data storage as it follows the key-value pair way of storing data similar to JSON data. NoSQL database are highly preferred for large data set (i.e for big data). Hbase is an example for this purpose.
  • For scalability: In most typical situations, SQL databases are vertically scalable. You can manage increasing load by increasing the CPU, RAM, SSD, etc, on a single server. On the other hand, NoSQL databases are horizontally scalable. You can just add few more servers easily in your NoSQL database infrastructure to handle the large traffic.
  • For high transactional based application: SQL databases are best fit for heavy duty transactional type applications, as it is more stable and promises the atomicity as well as integrity of the data. While you can use NoSQL for transactions purpose, it is still not comparable and sable enough in high load and for complex transactional applications.
  • For support: Excellent support are available for all SQL database from their vendors. There are also lot of independent consultations who can help you with SQL database for a very large scale deployments. For some NoSQL database you still have to rely on community support, and only limited outside experts are available for you to setup and deploy your large scale NoSQL deployments.
  • For properties: SQL databases emphasizes on ACID properties ( Atomicity, Consistency, Isolation and Durability) whereas the NoSQL database follows the Brewers CAP theorem ( Consistency, Availability and Partition tolerance )
  • For DB types: On a high-level, we can classify SQL databases as either open-source or close-sourced from commercial vendors. NoSQL databases can be classified on the basis of way of storing data as graph databases, key-value store databases, document store databases, column store database and XML databases.

SQL Database Examples

1. MySQL Community Edition

MySQL database is very popular open-source database. It is generally been stacked with apache and PHP, although it can be also stacked with nginx and server side javascripting using Node js. The following are some of MySQL benefits and strengths:

  • Replication: By replicating MySQL database across multiple nodes the work load can be reduced heavily increasing the scalability and availability of business application
  • Sharding: MySQL sharding os useful when there is large no of write operations in a high traffic website. By sharding MySQL servers, the application is partitioned into multiple servers dividing the database into small chunks. As low cost servers can be deployed for this purpose, this is cost effective.
  • Memcached as a NoSQL API to MySQL: Memcached can be used to increase the performance of the data retrieval operations giving an advantage of NoSQL api to MySQL server.
  • Maturity: This database has been around for a long time and tremendous community input and testing has gone into this database making it very stable.
  • Wide range of Platforms and Languages: MySql is available for all major platforms like Linux, Windows, Mac, BSD and Solaris. It also has connectors to languages like Node.js, Ruby, C#, C++, C, Java, Perl, PHP and Python.
  • Cost effectiveness: It is open source and free.

2. MS-SQL Server Express Edition

It is a powerful and user friendly database which has good stability, reliability and scalability with support from Microsoft. The following are some of MS-SQL benefits and strengths:

  • Integrated Development Environment: Microsoft visual studio, Sql Server Management Studio and Visual Developer tools provide a very helpful way for development and increase the developers productivity.
  • Disaster Recovery: It has good disaster recovery mechanism including database mirroring, fail over clustering and RAID partitioning.
  • Cloud back-up: Microsoft also provides cloud storage when you perform a cloud-backup of your database

3. Oracle Express Edition

It is a limited edition of Oracle Enterprise Edition server with certain limitations. This database is free for development and deployment. The following are some of Oracle benefits and strengths:

  • Easy to Upgrade: Can be easily upgraded to newer version, or to an enterprise edition.
  • Wide platform support: It supports a wide range of platforms including Linux and Windows
  • Scalability: Although the scalability of this database is not cost effective as MySQL server, but the solution is very reliable, secure, easily manageable and productive.

NoSQL Database Examples

1. MongoDB

Mongodb is one of the most popular document based NoSQL database as it stores data in JSON like documents. It is non-relational database with dynamic schema. It has been developed by the founders of DoubleClick, written in C++ and is currently being used by some big companies like The New York Times, Craigslist, MTV Networks. The following are some of MongoDB benefits and strengths:

  • Speed: For simple queries, it gives good performance, as all the related data are in single document which eliminates the join operations.
  • Scalability: It is horizontally scalable i.e. you can reduce the workload by increasing the number of servers in your resource pool instead of relying on a stand alone resource.
  • Manageable: It is easy to use for both developers and administrators. This also gives the ability to shard database
  • Dynamic Schema: Its gives you the flexibility to evolve your data schema without modifying the existing data

2. CouchDB

CouchDB is also a document based NoSQL database. It stores data in form of JSON documents. The following are some of CouchDB benefits and strengths:

  • Schema-less: As a member of NoSQL family, it also have dynamic schema which makes it more flexible, having a form of JSON documents for storing data.
  • HTTP query: You can access your database documents using your web browser.
  • Conflict Resolution: It has automatic conflict detection which is useful while in a distributed database.
  • Easy Replication: Implementing replication is fairly straight forward

3. Redis

Redis is another Open Source NoSQL database which is mainly used because of its lightening speed. It is written in ANSI C language. The following are some of Redis benefits and strengths:

  • Data structures: Redis provides efficient data structures to an extend that it is sometimes called as data structure server. The keys stored in database can be hashes, lists, strings, sorted or unsorted sets.
  • Redis as Cache: You can use Redis as a cache by implementing keys with limited time to live to improve the performance.
  • Very fast: It is consider as one of the fastest NoSQL server as it works with the in-memory dataset.
By vichhaiy Posted in DB

Backup & Restore database using command “mysqldump”.

  1. How to backup selected databases

Raised “wamp” server as an example:

C:\Users\Test>cd c:\wamp\bin\mysql\mysql15.1.53\bin

c:\wamp\bin\mysql\mysql15.1.53\bin>mysqldump.exe –u root database-name > c:\where-to-store-databases.sql

  1. How to backup all databases
  2. c:\wamp\bin\mysql\mysql15.1.53\bin>mysqldump.exe –u root –all-databases > c:\where-to-store-databases-all.sql
  3. How to restore:

c:\wamp\bin\mysql\mysql15.1.53\bin>mysqldump.exe –u root –all-databases < c:\where-to-store-databases-all.sql