Python PostgreSQL – Limit


Python PostgreSQL – Limit



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While executing a PostgreSQL SELECT statement you can limit the number of records in its result using the LIMIT clause.

Syntax

Following is the syntax of the LMIT clause in PostgreSQL −


SELECT column1, column2, columnN
FROM table_name
LIMIT [no of rows]

Example

Assume we have created a table with name CRICKETERS using the following query −


postgres=# CREATE TABLE CRICKETERS (
   First_Name VARCHAR(255), Last_Name VARCHAR(255), 
   Age int, Place_Of_Birth VARCHAR(255), Country VARCHAR(255)
);
CREATE TABLE
postgres=#

And if we have inserted 5 records in to it using INSERT statements as −


postgres=# insert into CRICKETERS values (''Shikhar'', ''Dhawan'', 33, ''Delhi'', ''India'');
INSERT 0 1
postgres=# insert into CRICKETERS values (''Jonathan'', ''Trott'', 38, ''CapeTown'', ''SouthAfrica'');
INSERT 0 1
postgres=# insert into CRICKETERS values (''Kumara'', ''Sangakkara'', 41, ''Matale'', ''Srilanka'');
INSERT 0 1
postgres=# insert into CRICKETERS values (''Virat'', ''Kohli'', 30, ''Delhi'', ''India'');
INSERT 0 1
postgres=# insert into CRICKETERS values (''Rohit'', ''Sharma'', 32, ''Nagpur'', ''India'');
INSERT 0 1

Following statement retrieves the first 3 records of the Cricketers table using the LIMIT clause −


postgres=# SELECT * FROM CRICKETERS LIMIT 3;
 first_name | last_name  | age | place_of_birth | country
------------+------------+-----+----------------+-------------
 Shikhar    | Dhawan     | 33  | Delhi          | India
 Jonathan   | Trott      | 38  | CapeTown       | SouthAfrica
 Kumara     | Sangakkara | 41  | Matale         | Srilanka

   (3 rows)

If you want to get records starting from a particular record (offset) you can do so, using the OFFSET clause along with LIMIT.


postgres=# SELECT * FROM CRICKETERS LIMIT 3 OFFSET 2;
 first_name | last_name  | age | place_of_birth | country
------------+------------+-----+----------------+----------
 Kumara     | Sangakkara | 41  | Matale         | Srilanka
 Virat      | Kohli      | 30  | Delhi          | India
 Rohit      | Sharma     | 32  | Nagpur         | India

   (3 rows)
postgres=#

Limit Clause Using Python

Following python example retrieves the contents of a table named EMPLOYEE, limiting the number of records in the result to 2 −


import psycopg2
#establishing the connection
conn = psycopg2.connect(
   database="mydb", user=''postgres'', password=''password'', host=''127.0.0.1'', port= ''5432''
)

#Setting auto commit false
conn.autocommit = True

#Creating a cursor object using the cursor() method
cursor = conn.cursor()

#Retrieving single row
sql = ''''''SELECT * from EMPLOYEE LIMIT 2 OFFSET 2''''''

#Executing the query
cursor.execute(sql)

#Fetching the data
result = cursor.fetchall();
print(result)

#Commit your changes in the database
conn.commit()

#Closing the connection
conn.close()

Output


[(''Sharukh'', ''Sheik'', 25, ''M'', 8300.0), (''Sarmista'', ''Sharma'', 26, ''F'', 10000.0)]

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