Introduction to PostgreSQL Data Types
PostgreSQL data types are used at the time of table creation for each column we need to specify a data type. The data type defines which type of data we have inserted in the table, we have created validation of data using PostgreSQL data types. Data types will decide what type of data we want to store in the field, data types are very important in PostgreSQL. In PostgreSQL users can create their own data types. In PostgreSQL, there are different categories of data types available. In PostgreSQL, there are different types of data types available. The database of any system has been considered as the base that stores every detail of the system.
All the application that operates using the data must have a database where all of the application related to data are stored. As we know that the data has been considered a very crucial part of any system, there must exist some platform that can help in processing and managing the data. The data type may be defined as a kind of data. In simple terms, the variable that is assigned with one of the data types can store the value of that data type only. For instance, if any variable is supposed to store the integer values only then in all the cases it will store the integer value only. If the user tries to feed the value of different data types in that variable, it will lead to the error.
Different PostgreSQL Data Types
Given below are different PostgreSQL Types:
- Numeric data types
- Monetary data types
- Character data types
- Binary data types
- Date/Time data types
- Boolean data types
- Enumerated data types
1. Numeric Data Types
PostgreSQL mainly provides two distinct types of numeric data types.
- Integer
- Floating point numbers
Integer Data Type
The variable defined with the integer data type can only store the integer value. The value must be the integer value else it will end up with throwing the error. For example, if a variable named i is supposed to store the integer value then it will hold the integer value only.
Example: – 1,200,459,354 etc.
In PostgreSQL basically three kinds of integer present are as follows:
- Small Integer: The storage size of the small integer is 2 bytes.
Range of small integer is -32768 to +32767
- Integer: Storage size of integer is 4 bytes.
Range of integer is -2147483648 to +2147483647
- Big Integer: Storage size of big integer is 8 bytes.
Range of big integer is -9223372036854775808 to 9223372036854775807
Code:
# create table num_test (id smallint, number int, salary bigint);
Output:
Floating point number
Floating-point numbers mainly divide in three types are as follows:
- Float
- Numeric
- Real or float8
Float: This is floating point number precision in PostgreSQL. Range if floating point is at least n and a maximum of 8 bytes. It is also called as double-precision data types.
Numeric: This is a real number data type in PostgreSQL. Numeric p and s are the exact numbers in numeric data types.
Real: It is a 4-byte floating point no in PostgreSQL data types.
Code:
# create table num_test1 (id real, number numeric, salary float);
Output:
2. Monetary Data Types
Monetary data types in PostgreSQL stores the current amount with a fractional fixed precision number. Range of monetary data type in PostgreSQL is -92233720368547758.08 to +92233720368547758.07
Code:
# create table mon_test (salary money, currency money);
Output:
3. Character Data Types
In PostgreSQL, there are mainly three distinct character data types available.
- Char
- Varchar
- Text
Char Data Type: The char data type is used to store a single character value. It is usually preferred to be used at the place where it needs to store just a single character. In case if the user tries to put more than one character in this, it will lead to an error. The variable storing the char values occupies very little space of the storage.
Example: ‘A’, ‘a’, ‘m’ etc
Text Data Type: The variable with data type as the text is capable of storing the long string values. In all the cases where the length of the text that has to be stored is unknown, one can use the text data type. It is also known as a variable-length character string in PostgreSQL. In these data types, text data is called a character string with unlimited records.
Example: “Hello”, “Congrats” etc
Varchar(n) Data Type: Varchar data type with some number written along with it denotes that it is capable of storing or holding only the number of characters that is written next to it. In this data types, we can store n number of characters.
For example, if we write varchar(9), it means that the variable will only be able to hold the maximum of nice characters.
Example: “ABCDEFGHI”, “Hello Hey”
Code:
# create table char_test (first_name char(10), middle_name varchar(20), last_name text);
Output:
4. Binary Data Types
PostgreSQL binary data types allow the storage of binary string in PostgreSQL. Its variable length is binary data types.
Code:
# create table bin_test (id bytea, dept_no bytea, salary bytea);
Output:
5. Date/Time data Types
The time data type is assigned to the variable that is supposed to store only the time value. There should be some particular format of time that has to be stored in the time data type variable. It is one of the most important data types in PostgreSQL as it is used to keep track of the transactions.
Example: 12:00:36, 01:06:56
Below is the date/time data types available in PostgreSQL are as follows:
- Date
- Time
- Timestamp
- Timestamptz
- Interval
Date: This data type only stores date. It will not store any time. The low value of this data type is 4713 BC and the highest value is 294276 AD.
Time: This data type only stores time. It will not store any date. The low value of this data type is 4713 BC and the highest value is 5874897 AD.
Timestamp: This data type stores the date and time. It will not store any timestamp. The low value of this data type is 4713 BC and the highest value is 294276 AD.
Timestamptz: This data type stores the date and time with the timestamp. The low value of this data type is 4713 BC and the highest value is 294276 AD.
Interval: The storage size of these data types is 12 bytes. It will describe the time interval value.
Code:
testing=# create table dt_test (start_date date, start_time time, completion_time timestamp, completion_date timestamptz, no_of_year interval);
Output:
6. Boolean Data Types
Boolean is one of the data types supported by PostgreSQL. This data type can store two values only that are “True” and “False”. In usual cases, the Boolean values are used to verify if the statement is correct as when the statement is correct, it returns the true value else the value will be false. This data type is also used while decision making and based on either of the two values, the decision has to be taken by the program.
Example: “True”, “False”
Code:
# create table boolean_test (status boolean, flag boolean, state boolean);
Output:
7. Enumerated Data Types
Enumerated data types in PostgreSQL comprises a static order set of values. This is closely similar to the enum data types which was supported in the programming language. Enumerated data type in PostgreSQL creates using create type command. In PostgreSQL, if we create enumerated data types once it will use in any other type.
Code:
# CREATE TYPE year AS ENUM ('JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL', 'AUG', 'SEP', 'OCT', 'NOV', 'DEC');
Output:
Some other Data Types in PostgreSQL
- Interval Data Type: The variable that is assigned with the interval data type is capable to store a particular time interval. It is concerned about the time and can be used to estimate the time in several cases. In the database, it is sincerely observed that which transaction has taken place at what interval and this data type helps us to manage the intervals. Example – ‘7 months ago’, ‘2 year 5 hours 40 minutes’
- Array: The array is used to store the set of string or set of any values but the only restriction is, all the values in the array have to be of the same data type. Using the array makes the program ample convenient to be understood by everyone who was not the part while code was developed. Example – ARRAY [ 408)-589-5846′,'(408)-589-5555′ ]
- UUID Data Type: The UUID data type is used to store the Universally Unique Identifiers which are actually the values that are used throughout the program to uniquely identify anything. It is a special kind of data type that cannot be found in high-level programming languages. Example – 0e37df36-f698-11e6-8dd4–cb9ced3df976, a81bc81b-dead-4e5d-abff-90865d1e13b1
- JSON Data Type: The variable that is supposed to store the JSON values are assigned with the JSON data type. It is one of the most important data types used in PostgreSQL that is capable of holding the complex JSON data. Example – { “client”: “Doe”, “items”: {“product”: “Application”,”qty”: 7}}
Conclusion
The PostgreSQL database management can be considered very useful while used for any application that has to work with the data. It has been designed to work with several kinds of data types where all the data types hold its own importance. Also, in order to keep track of the time while the transactions are done, there is data types like time, date, interval, etc. are present. In some of the operating systems like Kali Linux, PostgreSQL is available inbuilt. It makes it very easy for the developers to integrate their application with the database and they can also use the different types of data types that have been made available in PostgreSQL.
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