PostgreSQL tutorial

Preamble

PostgreSQL is a powerful Open Source Object-Relational Database System. It has over 15 years of the active development phase and a proven architecture that has earned a good reputation for reliability, data integrity, and accuracy.

This tutorial will give you a quick start with PostgreSQL and allows you to get used to PostgreSQL programming.
PostgreSQL data types
Literals
Announcement of variables
Comments
Aliases (pseudonyms)

PostgreSQL functions

PostgreSQL function date/time

Function & Description
AGE The age PostgreSQL function returns the number of years, months, and days between two dates.
CURRENT_DATE The current_date function in PostgreSQL returns the current date.
CURRENT_TIME The current_time function in PostgreSQL returns the current time with time zone.
CURRENT_TIMESTAMP The current_timestamp PostgreSQL function returns the current date and time with the time zone.
DATE_PART The date_part PostgreSQL function extracts parts from the date.
EXTRACT The extract PostgreSQL function extracts parts from the date.
LOCALTIME The local time PostgreSQL function returns the current time.
LOCALTIMESTAMP The localtimestamp PostgreSQL function returns the current date and time.
NOW The now PostgreSQL function returns the current time and date with the time zone.

PostgreSQL string functions

Function & Description
BTRIM The PostgreSQL btrim function removes all specified characters both at the beginning and at the end of a line.
CHAR_LENGTH The char_length function in PostgreSQL returns the length of the specified string.
CHARACTER_LENGTH The character_length function in PostgreSQL returns the length of the specified string.
INITCAP The function initcap PostgreSQL converts the first letter of each word to upper case, and all other letters are converted to lower case.
LENGTH The length PostgreSQL function returns the length of the specified string, expressed in the number of characters.
LOWER The lower PostgreSQL function converts all characters of a specified string into lower case.
LPAD The PostgreSQL lpad function returns a string added to the left side of the specified string of a certain length.
LTRIM The ltrim PostgreSQL function removes all specified characters on the left side of the line.
POSTGRESQL operator \|\| PostgreSQL operator \|\| allows to combine 2 or more lines together.
POSITION The PostgreSQL position function returns the substring location in a string.
REPEAT The repeat PostgreSQL function repeats the string as many times as specified.
REPLACE The replace PostgreSQL function replaces all occurrences of the specified string.
RPAD The PostgreSQL rpad function returns a string added to the right side of the specified string of a certain length.
RTRIM The PostgreSQL rtrim function removes all specified characters on the right side of the line.
STRPOS The PostgreSQL strpos function returns the substring arrangement in a string.
SUBSTRING The substring PostgreSQL function allows extracting substring from a string.
TRANSLATE The translate PostgreSQL function replaces a sequence of characters in a string with another set of characters. However, it replaces one character at a time. For example, it replaces the first character in string_to_replace with the first character in replace_string. Then it will replace the second character in string_to_replace with the second character in replace_string, etc.
TRIM The trim PostgreSQL function removes all specified characters from the beginning or end of a line.
UPPER PostgreSQL function upper converts all characters in a specified string into upper case.

PostgreSQL conversion functions

Function & Description
TO_CHAR The PostgreSQL to_char function converts a number or date to a string.
TO_DATE The to_date function in PostgreSQL converts a string into a date.
TO_NUMBER The PostgreSQL to_number function converts a string into a number.
TO_TIMESTAMP The PostgreSQL to_timestamp function converts a string into a timestamp.

Numerical/mathematical PostgreSQL functions

Function & Description
ABS The abs function in PostgreSQL returns the absolute value of the number.
AVG The avg PostgreSQL function returns the average value of the expression.
CEIL The ceil PostgreSQL function returns the smallest integer value, which is greater than or equal to a number.
CEILING The ceiling PostgreSQL function returns the smallest integer value, which is greater than or equal to a number.
COUNT The count PostgreSQL function returns the number of expressions.
DIV The div PostgreSQL function is used for integer division, where n is divided by m and integer value is returned.
EXP The exp function in PostgreSQL returns e, raised to number (or enumber).
FLOOR The floor PostgreSQL function returns the largest integer value that is less than or equal to a number.
MAX The function max PostgreSQL returns the maximum value of the expression.
MIN The min function in PostgreSQL returns the minimum value of the expression.
MOD The mod PostgreSQL function returns the residue from n divided by m.
POWER The power PostgreSQL function returns the value of m, which is elevated to n-th degree.
RANDOM The random PostgreSQL function can be used to return a random number or a random number within a range.
ROUND The round PostgreSQL function returns a number rounded to a certain number of decimal places.
SETSEED The setseed PostgreSQL function can be used to set the initial number the next time the random function is called. If you do not call setseed, PostgreSQL will use its own seed value. This may or may not be really random. If you set the initial value by calling setseed, then random will return a repeatable sequence of random numbers obtained from the initial number. Tip: The setseed function can be very useful in situations where you want to make sure that PostgreSQL uses a really random starting number.
SIGN The sign PostgreSQL function returns a value that denotes a number sign.
SQRT The function sqrt PostgreSQL returns the square root of the number.
SUM The sum PostgreSQL function returns the cumulative value of the expression.
TRUNC The trunc PostgreSQL function returns a number truncated to a certain number of decimal places.

PostgreSQL query types

SELECT	Get records from the table
SELECT LIMIT	Get records from the table and limit the number of records
DISTINCT	Used to remove duplicates from the result set
FROM	Used for displaying tables and any associations
WHERE	Used to filter the results
ORDER BY	Used to sort the results
GROUP BY	Used to group the results
HAVING	Used in combination with the GROUP BY operator to limit groups of returned strings only to those whose TRUE condition
INSERT	Operator for inserting a row into a table
UPDATE	The operator of data update in the table
DELETE	Operator to delete data from the table
UNION	Operator to combine sets of results with the removal of repeating rows
UNION ALL	Operator to combine sets of results without removing repeating lines
INTERSECT	The operator returns the general records of the result sets
EXCEPT	Set of results from one minus set of results from another
Subqueries	Attached request (subquery)
JOIN Tables	Used to extract data from multiple tables

PostgreSQL database administration

Create User	Create a database account
Grant/Revoke Privileges	Granting and cancellation of privileges in the database
Change Password	Change user password
Find Users	User search
Find Users Logged In	Find users who are logged in to PostgreSQL
Rename User	Rename user
Drop User	Delete user
Vacuum	Cleaning up unused space in the database
Auto_Vacuum	The process that automatically cleans unused space in the database

PostgreSQL tables and views

CREATE TABLE	Create a table
CREATE TABLE AS	Create a table from the data of another table
ALTER TABLE	Add, edit, delete columns in the table; rename the table
DROP TABLE	Delete the table
TRUNCATE TABLE	Delete all records from the table (with the optimizer)
VIEW	Virtual table (representation of other tables)

PostgreSQL keys, indexes, and restrictions

Primary Keys	Create, add and delete primary keys
Indexes	Create, delete and rename indices (performance tuning)
Unique Constraints	Create, add and remove unique constraints

PostgreSQL conditions

AND	Logical operator AND
OR	Logical operator OR
AND and OR	Logical operator AND and OR
LIKE	Determines whether the specified character string coincides with the specified template
IN	Determines whether a specified value matches a value in a nested query or list
NOT	Negation of conditions
IS NULL	Used to check the NULL value
IS NOT NULL	Used to check the NOT NULL value
BETWEEN	Defines the range to check the condition
EXISTS	In the WHERE proposal of an external query, the presence of strings returned by an attached query is checked.

PostgreSQL comparison statements

Comparison Operators

Comparison operators such as =, <>, !=, >, < and others

Learn PostgreSQL Tutorial – Full Course for Beginners

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