![]() In the above example, we use a drop table if it exists.Similarly, we will drop our second table using a drop table statement containing foreign key constraints as follows. Drop table statement deletes the whole table from the database and directly deletes the table.In this example, the sample table does not contain any foreign key we show how to drop the foreign key constraints using a drop table statement. In the above example, we use drop table statements to drop foreign key constraints in which that sample is the specified table name from the database that we need to drop.Let’s see a different example of a drop table as follows. See here when we use the above syntax, it deletes tables from databases, not particular foreign key columns, but when we use alter table statements, we can delete specific foreign key constraints.In the above syntax, we drop table statements to drop the foreign key constraint where if exists means a specified table is present in a database and table name means specified table name from the database.In this example, table name details and the foreign key name is fk_sample that we need to drop from the database table.Īnother way to delete foreign keys is that you can drop tables if they exist. In the above example, we use an alter table statement to drop foreign key constraints from the database table.Example #2Ĭode: alter table details drop constraint fk_sample So now, let’s see how we can drop the foreign key constraint by using the following statement as follows. In both examples above, we created two tables: samples and details for implementing foreign key constraint. So we delete the first record by using the following statement as follows. In the above example, we insert two duplicate records into the table but violate the foreign key constraint. See here we insert the same records into the table, as shown in the statement. With the help of the above insert statement, we insert records into the details table.Now we insert records into the details table using the following statement.Ĭode: insert into details(emp_id, cust_name, cust_phone, cust_email) With the help of the above statement, we created details tables with different attributes such as cust_id, cust_name, cust_phone, and cust_email, and here, we created a foreign key name as emp_id with reference to the sample table.Now we create another table by using the following statement as follows.Ĭust_id INT GENERATED ALWAYS AS IDENTITY, With the help of the above statement, we insert two records into a sample table.Now we insert a record into the sample table using the following statement. Illustrate the end result of the above declaration by using the following snapshot.In the above example, we use a create table to create a sample table with two attributes such as emp_id and emp_name, and here we assign the primary key to emp_id as shown in the statement.Let’s see how we can implement foreign key constraints, and we will also see how to drop foreign key from database tables.įirst, we need a foreign key to perform a drop foreign key constraint, so let’s see how to create a foreign key as follows. We can perform different operations on tables with the help of psql and pgAdmin.Need basic knowledge about the foreign key, that means how it is used.We must require a database table to perform foreign key constraints.Require basic knowledge about PostgreSQL and the key constraints of the database table.We must install PostgreSQL in our system.How to drop the foreign key in PostgreSQL? Also, the key name means the actual foreign key name from the table we won’t drop. In the above syntax, we use the alter table statement to drop foreign key constraint where table_name means specified table name from the database, and drop is used to delete the foreign key control from a database table.Syntax: Alter table table_name drop constraint key name Hadoop, Data Science, Statistics & others
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