Definition of PostgreSQL Limit Offset
PostgreSQL provides limit and offset clauses to users to perform different operations on database tables as per requirement. The limit and offset used when we want to retrieve only specific rows from the database. The LIMIT clause returns only specific values which are written after the LIMIT keyword. On the other hand OFFSET clause is used to skip any number of records before starting to return records from the database table. That means some time the user does not need to display some records at that time we use OFFSET clause in query.
Syntax:
select column name1, column name2, column name N, from table name [order by clause Sort Expression….] [LIMIT number of count(value)][OFFSET number of count(value)]
Explanation: With the help of above syntax we are to implement LIMIT and OFFSET clauses in PostgreSQL. In the above syntax we use select clause then column name means column names that we want to print from the table then pass LIMIT value and OFFSET value.
How does Limit Offset Work in PostgreSQL?
- We must install PostgreSql in your system.
- We required basic knowledge about PostgreSql.
- We must require a database table to perform LIMIT and OFFSET.
- We must need basic knowledge about the LIMIT and OFFSET syntax that means how it is used.
- We can perform different operations on database tables with the help of psql and pgAdmin.
Examples to Implement PostgreSQL Limit Offset
Let’s see how we can implement LIMIT and OFFSET by using the following example as follows.
Example #1
Using LIMIT
First we create a table employee by using the following statement as follows.
create table employee (emp_id serial PRIMARY KEY, emp_name varchar(30), emp_dept varchar[],emp_city varchar[],emp_salary text[]);
Explanation:
With the help of the above statement we created an employee table with different attributes such as emp_id, emp_name, emp_dept, emp_city and emp_salary. Illustrate the end result of the above declaration by using the following snapshot.
After that we insert some records into the employee database table by using the following statement as follows.
Insert into employee (emp_name, emp_dept, emp_city, emp_salary)
Values
('Jacson', '{"comp"}' , '{"City W"}', '{"40000"}'),
('Paul', '{"mech"}', '{"City A"}', '{"20000"}'),
('sam', '{"Account"}', '{"City B"}', '{"10000"}'),
('John', '{"Purchase"}', '{"City C"}', '{"30000"}');
Explanation:
Illustrate the end result of the above declaration by using the following snapshot.
So let’s see a simple LIMIT clause implemented as follows.
First count rows in the database table by using the following statement as follows.
select count(*) from public."employee";
Illustrate the end result of the above declaration by using the following snapshot.
Then apply LIMIT clause
select * from public."employee" limit 2;
Explanation:
When we use LIMIT in a statement at that time to add ORDER BY clause that is useful to return the result in specific order. Otherwise you will get unexpected results. In the above example the database table employee has 4 records as shown in the previous snapshot after applying LIMIT 2. Illustrate the end result of the above declaration by using the following snapshot.
Example #2
Using OFFSET
When we use OFFSET clause it returns records after OFFSET value and it skips rows before OFFSET value.
select * from public."employee" ;
Explanation:
When we execute the above statement it shows all records of the database table. Illustrate the end result of the above declaration by using the following snapshot.
select * from public."employee" offset 2 ;
Explanation:
In the above example the database table employee has 4 records but when we use OFFSET with value 2 so it skips the first two rows from the database table and returns remaining records. Illustrate the end result of the above declaration by using the following snapshot.
Example #3
Using LIMIT and OFFSET clause in same statement
select * from public."employee" offset 2 limit 1 ;
Explanation:
In this example we use both LIMIT and OFFSET clauses in the same statement here we use OFFSET value is 2 and LIMIT 1. In the employee database table has 4 records, OFFSET skips first 2 records and then uses LIMIT 1. Illustrate the end result of the above declaration by using the following snapshot.
When we use LIMIT with 2. Illustrate the end result of the above declaration by using the following snapshot.
Example #4
Using LIMIT, OFFSET and ORDER BY clause.
select * from public."employee" order by "emp_salary" offset 3 limit 1 ;
Explanation:
In this example, we used ORDER BY clause. Illustrate the end result of the above declaration by using the following snapshot.
Example #5
If the database doesn’t have sufficient records in the database table.
select * from public."employee" order by "emp_salary" limit 5 ;
Explanation
If the number of records not present in the database table at that time LIMIT returns all records from the database table. Illustrate the end result of the above declaration by using the following snapshot.
Some tips about LIMIT and OFFSET as follows
- When we use LIMIT 0 it is used to return number columns in the database table.
Example:
select * from public."employee" limit 0 ;
Explanation: In the above example we use LIMIT 0. Illustrate the end result of the above declaration by using the following snapshot.
- When we use the LIMIT clause with ALL then it returns all records from the database table.
Example:
select * from "employee" limit ALL ;
Explanation: In the above example we use the LIMIT clause with ALL. Illustrate the end result of the above declaration by using the following snapshot.
- When we use the OFFSET clause with 0 values in the statement it returns all records from the database table.
Example:
select * from "employee" offset 0;
Explanation: In the above example we use OFFSET clauses with value. Illustrate the end result of the above declaration by using the following snapshot.
Uses of PostgreSQL Limit Offset
- LIMIT clause is used to retrieve specific records from the database table means maximum records.
- OFFSET clause is used to skip records from the result.
- EXECUTION of LIMIT and OFFSET are fast so most applications use LIMIT and OFFSET.
Conclusion
We hope from the above article you have understood about the PostgreSQL LIMIT and OFFSET clause from the above article we learn the basic syntax of LIMIT and OFFSET clause then we also learn how we can use LIMIT and OFFSET clause by using different methods with examples. From this article, we learn how we can handle LIMIT and OFFSET clauses correctly.
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