Use alter table to drop a column from an existing table. Use the alter table command to add a column to an existing table. You can use alter table to modify a remote table using Component Integration Services (CIS). If a database has any objects (stored procedures, triggers, and so on) that perform a select * on a table from which you have dropped a column, an error message lists the missing column. Objects Using select * Do Not List Changes to Table.
ALTER TABLE ADD COLUMN HOW TO
In this tutorial, you have learned how to use the PostgresSQL ADD COLUMN statement to add one or more columns to a table.
ALTER TABLE ADD COLUMN CODE
ALTER TABLE customersĪLTER COLUMN contact_name SET NOT NULL Code language: SQL (Structured Query Language) ( sql ) Third, set the NOT NULL constraint for the contact_name column. SET contact_name = 'Lily Bush' WHERE id = 3 Code language: SQL (Structured Query Language) ( sql ) SET contact_name = 'Mary Doe' WHERE id = 2 SET contact_name = 'John Doe' WHERE id = 1
ALTER TABLE ADD COLUMN UPDATE
Second, update the values in the contact_name column. When PostgreSQL added the column, this new column receive NULL, which violates the NOT NULL constraint.įirst, add the column without the NOT NULL constraint: ALTER TABLE customersĪDD COLUMN contact_name VARCHAR Code language: SQL (Structured Query Language) ( sql )
This is because the contact_name column has the NOT NULL constraint. PostgreSQL issued an error: ERROR: column "contact_name" contains null values Code language: SQL (Structured Query Language) ( sql ) Suppose that you want to add the contact_name column to the customers table: ALTER TABLE customersĪDD COLUMN contact_name VARCHAR NOT NULL Code language: SQL (Structured Query Language) ( sql ) ( 'Sony') Code language: SQL (Structured Query Language) ( sql ) The following statement inserts data into the customers table. Add a column with the NOT NULL constraint to a table that already has data To view the structure of the customers table in the psql tool, you can use the \d command like this: \d customers Code language: SQL (Structured Query Language) ( sql )Īs can be seen clearly from the output, the phone, fax, and email columns appeared at the end of the column list of the customers table. The following statement uses the ALTER TABLE ADD COLUMN statement to add the phone column to the customers table: ALTER TABLE customersĪDD COLUMN phone VARCHAR Code language: SQL (Structured Query Language) ( sql )Īnd the following statement adds the fax and email columns to the customers table: ALTER TABLE customersĪDD COLUMN email VARCHAR Code language: SQL (Structured Query Language) ( sql ) ) Code language: SQL (Structured Query Language) ( sql )
The following CREATE TABLE statement creates a new table named customers with two columns: id and customer_name: DROP TABLE IF EXISTS customers CASCADE To add multiple columns to an existing table, you use multiple ADD COLUMN clauses in the ALTER TABLE statement as follows: ALTER TABLE table_nameĪDD COLUMN column_name1 data_type constraint,ĪDD COLUMN column_name2 data_type constraint,ĪDD COLUMN column_namen data_type constraint Ĭode language: SQL (Structured Query Language) ( sql ) PostgreSQL ADD COLUMN statement examples
PostgreSQL has no option to specify the position of the new column in the table.
When you add a new column to the table, PostgreSQL appends it at the end of the table. Second, specify the name of the new column as well as its data type and constraint after the ADD COLUMN keywords.First, specify the name of the table that you want to add a new column to after the ALTER TABLE keyword.To add a new column to an existing table, you use the ALTER TABLE ADD COLUMN statement as follows: ALTER TABLE table_nameĪDD COLUMN new_column_name data_type constraint Code language: SQL (Structured Query Language) ( sql ) Introduction to the PostgreSQL ADD COLUMN statement Summary: in this tutorial, you will learn how to use the PostgreSQL ADD COLUMN statement to add one or more columns to an existing table.
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