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To find the name of a constraint in PostgreSQL, use the view pg_constraint in the pg_catalog schema. We want to display the names of the constraints in the table student. Here we are going to use the fruit_sell table and the records or information of the table is given below.You want to find the names of the constraints in a table in PostgreSQL. In Postgresql, we will use the DISTINCT in the select statement to find the unique data or values in a column. ALTER TABLE unique_dataĪlso, check: Postgresql Add Foreign Key Postgresql unique select Now add a unique constraint to the unique_data table using the unique_data_id index using the below code. CREATE UNIQUE INDEX CONCURRENTLY unique_data_id In the above code, we are creating a table unique_data with three columns id, name, unq_data_id.Ĭreate a unique index on unq_data_id.

Let’s create a new table name unique_data. In Postgresql, when we want to add a unique constraint to an existing column or group of columns. Read: PostgreSQL Update Join Postgresql unique index In the above output, we have inserted the records as states and cities like New York, California is the state of the United States and Victoria is the state of Australia. Postgresql unique constraint multiple columns VALUES('dan', output of the above code is given below.

INSERT INTO emp_data insert the same records with a different name. In the above code, we have declared column email as unique using the keyword UNIQUE. Let’s create a table with columns id, emp_name, email, and make the email column unique. When we add a UNIQUE constraint to a column or a group of columns, PostgreSQL will automatically create a unique index on the column or the group of columns. The same process is done for updating existing data. If the value already exists then It rejects the change and issues an error. When a UNIQUE constraint is in place, it tries to see if the value is already in the table before inserting a new entry. PostgreSQL provides us with the UNIQUE constraint that keeps the uniqueness of the data correctly.

In Postgresql, we want to ensure that values stored in a column or a group of columns are unique across the whole table such as email addresses or usernames.