Introduction to Standard Query Language (SQL) and PostgreSQL
Jul 25, 2017 · 2 min read

Below is a breakdown SQL definitions and syntax. Also a table showing some the more important datatypes supported in PostgreSQL
Definitions:
SQL — SQL (standard query language) is a standard language for storing, manipulating and retrieving data in databases. SQL can do the following:
- execute queries against a database
- retrieve data from a database
- insert records in a database
- update records in a database
- delete records from a database
- create new databases
- create new tables in a database
- create stored procedures in a database
- can create views in a database
- can set permissions on tables, procedures, and views
PostgreSQL — PostgreSQL is an Relational Database Management System (RDBMS) (such as MS Access, SQL Server, MySQL). The data in an RDBMS is stored in database objects called tables. A table is a collection of related data entries and it consists of columns and rows (as seen in the image below).
Important SQL commands:
SELECT — extracts data from a database
SELECT column1, column2, ...
FROM table_name;UPDATE — updates data in a database
UPDATE table_name
SET column1 = value1, column2 = value2, ...
WHERE condition;DELETE — deletes data from a database
DELETE FROM table_name
WHERE condition;INSERT INTO — inserts new data into a database
INSERT INTO table_name (column1, column2, column3, ...)
VALUES (value1, value2, value3, ...);CREATE DATABASE — creates a new database
CREATE DATABASE databasename;CREATE TABLE — creates a new table
CREATE TABLE table_name (
column1 datatype,
column2 datatype,
column3 datatype,
....
);ALTER TABLE — modifies a table
ALTER TABLE table_name
ADD column_name datatype;DROP TABLE — deletes a table
DROP TABLE table_name;CREATE INDEX — creates an index (search key)
CREATE INDEX index_name
ON table_name (column1, column2, ...);DROP INDEX — deletes an index
DROP INDEX index_name;Important Data Types (PostgreSQL):

