PostgreSQL – DELETE Query
The PostgreSQL DELETE Query is used to delete the existing records from a table. You can use WHERE clause with DELETE query to delete the selected rows. Otherwise, all the records would be deleted.
The basic syntax of DELETE query with WHERE clause is as follows −
DELETE FROM table_name WHERE [condition];
You can combine N number of conditions using AND or OR operators.
Consider the table COMPANY, having records as follows −
# select * from COMPANY; id | name | age | address | salary ----+-------+-----+-----------+-------- 1 | Paul | 32 | California| 20000 2 | Allen | 25 | Texas | 15000 3 | Teddy | 23 | Norway | 20000 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 6 | Kim | 22 | South-Hall| 45000 7 | James | 24 | Houston | 10000 (7 rows)
The following is an example, which would DELETE a customer whose ID is 7 −
testdb=# DELETE FROM COMPANY WHERE ID = 2;
Now, COMPANY table will have the following records −
id | name | age | address | salary ----+-------+-----+-------------+-------- 1 | Paul | 32 | California | 20000 3 | Teddy | 23 | Norway | 20000 4 | Mark | 25 | Rich-Mond | 65000 5 | David | 27 | Texas | 85000 6 | Kim | 22 | South-Hall | 45000 7 | James | 24 | Houston | 10000 (6 rows)
If you want to DELETE all the records from COMPANY table, you do not need to use WHERE clause with DELETE queries, which would be as follows −
testdb=# DELETE FROM COMPANY;
Now, COMPANY table does not have any record because all the records have been deleted by the DELETE statement.
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There are two sides to machine learning:
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- Theoretical Machine Learning: This is about math and abstraction and idealized scenarios and limits and beauty and informing what is possible. It is a whole lot neater and cleaner and removed from the mess of reality.
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