Suppose we have to alter the data type of the bike_model column from text to varchar and bike_number column from varchar to text. Following will be the syntax for multiple ALTER COLUMN commands: ALTER TABLE tab_nameĪLTER COLUMN col_name_1 TYPE modified_data_type,ĪLTER COLUMN col_name_2 TYPE modified_data_type,ĪLTER COLUMN col_name_N TYPE modified_data_type Įxample #1: How to Alter the Data Type of Multiple Columns? You have to use several ALTER COLUMN commands to alter the data type of multiple columns. How to Alter Multiple Column Type in PostgreSQL? The output shows that the column type has been altered successfully. Let’s run the SELECT command to see the updated table: SELECT * from bike_details The output shows that the bike_details table has been altered successfully. To do so, we will execute the below-given statement: ALTER TABLE bike_details Suppose we have to alter the type of bike_number column from text to varchar. Let’s run the SELECT query to fetch its details: SELECT * FROM bike_details We have created a bike_details table in our database. Next, specify either the “SET DATA TYPE” or “TYPE” keyword followed by the modified data type.Įxample: How to Alter the Column Type From TEXT to VARCHAR in PostgreSQL? Specify the column name to be altered after the ALTER COLUMN command. Specify the table name to be altered after the ALTER TABLE command. Here is a simple syntax for altering a single column type in PostgreSQL: ALTER TABLE tab_nameĪLTER COLUMN col_name TYPE modified_data_type This write-up will present a comprehensive guide on how to alter the column type in PostgreSQL. Multiple ALTER COLUMN commands will be used along with the ALTER TABLE command to alter the type of multiple columns in a single statement. In this blog, we have learned to change/modify the data type of columns in Postgres in detail.The “SET DATA TYPE'' or “TYPE” keyword is used with the collaboration of ALTER TABLE and ALTER COLUMN commands to alter/change the column type in PostgreSQL. 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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