![]() We use the “ALTER COLUMN” command to change the data type of a column.Ĭode: Alter table student ALTER COLUMN phone type varchar(10) The above syntax defines the alter table statement as changing the column data type. Syntax: Alter table name_of_tableALTER COLUMN name_of_column data_type Below is the syntax to change the data type. In the example below, we have to change the column’s data type. Drop constraint is used to drop constraint from the column.Ĭode: ALTER TABLE student DROP CONSTRAINT "student_pkey" The above syntax defines the alter table statement as a dropping constraint from the column. Syntax: Alter table name_of_tableDROP CONTRAINT name_of_constraint Below is the syntax of removing constraint. In the below example, we have to remove the constraint. Add column is defined as add a new column to an existing table.Ĭode: ALTER TABLE student ADD COLUMN address varchar In the above syntax, the alter table statement is defined as add the new column using the alter table statement. Syntax: Alter table name_of_tableADD COLUMN column_name (Name of column which we have adding) data_type Below is the syntax of the alter table to add a new column are as follows. In the example below, we added a new column to the table using the alter table statement. In the above example, we have to change the table column name from stud_name to stud_name_new. Rename column is defined as rename an existing column with a new name.Ĭode: ALTER TABLE student RENAME COLUMN stud_name TO stud_name_new ![]() In the above syntax, the alter table statement is defined as changing the column’s name using the alter table statement. Syntax Alter table existing_table_name RENAME COLUMN old_column_name TO new_column_name Below is the syntax of the alter table to change the name of the column. In the below example, we have used alter table command to change an existing column’s name. Below is the table description of the student and stud2 table.īelow is the method of the same: 1. In this blog, we have learned to change/modify the data type of columns in Postgres in detail.Using the stud2 and student table to describe the example of altering a column in PostgreSQL is as follows. One thing that is to be noticed is that we can not implicitly typecast the TEXT/VARCHAR data type into the INT data type, to do this we will need a USING clause. The column whose data type is to be altered is specified after the ALTER COLUMN statement and we have to specify the new data type after the TYPE or SET DATA clause. The table that needs to be altered needs to be specified in the query. We can change/modify the data type of a column or multiple columns by making use of the ALTER statement. In this way, we can change/modify the data type of the column/columns. We can see that the data type of the “phone_number” column has been changed from VARCHAR to INT. We can verify if the data type has changed or not by executing the SELECT statement. Now the query will work fine as it will alter the table for the change in the table’s column data type as given below: We will execute the SELECT statement to see what the table “account_details” looks like and what is the data type of the “user_name” column before changing: Step 1: Check the Current Data Type of the Column Let’s alter the data type of the column “user_name” from the table “account_details”. We can change/modify the data type of a Postgres column using an ALTER command. Example 1: Change/Modify Column Type in PostgreSQL Let’s learn how we can change the data type of any column in PostgreSQL. The data type that we want the column to be modified into is to be written after the “SET DATA” or “TYPE” keywords.The “ SET DATA” or “TYPE” keyword is used to set the data type to a new one.This command is followed by the “SET DATA” or “TYPE” keyword. The name of the column whose data type is to be altered is written after the ALTER COLUMN command.The ALTER COLUMN command is used to alter the column’s data type.The name of the table we want to alter is specified after the ALTER TABLE statement.The ALTER TABLE clause alters the table.
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