# How to Change/Modify Column Type in PostgreSQL

> In PostgreSQL, the “ALTER TABLE” and “ALTER COLUMN” commands, along with the TYPE Keyword, are used to change/modify the data type of any specific column.

In **PostgreSQL** , the **“ALTER TABLE”** and **“ALTER COLUMN”** commands, along with the **TYPE** Keyword, are used to change/modify the data type of a column. For example, integer to character, text to varchar, and so on. In **PostgreSQL** , we can change the data type of one or more than one column using the **“ALTER TABLE”** and **“ALTER COLUMN”** commands.

This blog will present a step-by-step guide on changing the column’s data type. So, without any further delay, let’s start.

 **How to Change/Update the Column’s Data Type in Postgres?**

The below-given syntax will assist you in changing the data type of any particular column:
    
    
    ALTER TABLE tab_name
    ALTER COLUMN col_name TYPE new_data_type;

Let’s analyze the above-given syntax step-by-step:

\- **tab_name** represents a table whose column will be altered.

\- **col_name** represents the column to be altered.

\- **TYPE** is a keyword.

\- **new_data_type** represents the altered/modified data type of the selected column.

 **Example: How to Change/Modify the Column’s Type From int to text?**

You have to follow the below-listed procedure to change the column’s data type:

 **Step 1: Access a Database**

Firstly, open SQL SHELL and type the “\c” command followed by the database name to make a connection with the selected database:
    
    
    \c example;

 **Step 2: Available Tables**

Once you are connected to the targeted database, type the **“\dt”** command to see the list of available tables in that database:
    
    
    \dt;

 **Step 3: Describe the Table**

Select a table and run the following command to see the structure of the selected table:
    
    
    \d team_info;

 **Step 4: Change Column Type**

Execute the below-given command to change the data type of the **“team_rating”** column from **“integer”** to **“character”** :
    
    
    ALTER TABLE team_info
    ALTER COLUMN team_rating TYPE VARCHAR(30);

 **Step 5: Verify the Column Type**

Let’s run the **“\d”** command followed by table name to see the changes made to the selected table:
    
    
    \d team_info;

The output authenticates that the data type of the **“team_rating”** column has been updated to the character type.

 **How to Change/Modify the Type of Several Columns With a Single Command?**

Follow the comma-separated syntax to change the data type of more than one column using a single query:
    
    
    ALTER TABLE tab_name
    ALTER COLUMN col_1 TYPE new_data_type,
    ALTER COLUMN col_2 TYPE new_data_type;

 **Example: How to update data types of several columns using a single command in PostgreSQL?**

From the snippet shown in step 4 of the previous example, we can observe that the **“team_rating”** and **“team_lead”** columns have a “character” data type. Suppose we have to change both columns' data types from character to text. To do so, we have to follow the below-given process:

 **Step 1: Change the Column Type**

We can change the type of selected columns by executing the following query/command:
    
    
    ALTER TABLE team_info
    ALTER COLUMN team_rating TYPE TEXT,
    ALTER COLUMN team_lead TYPE TEXT;

 **Step 2: Verify the Column Type**

Let’s execute the below-given command to check and verify the data type of the selected columns:
    
    
    \d team_info;

The snippet given above proved that the data type of the **“team_rating”** and **“team_lead”** columns have been successfully updated to the “text” data type.

 **Conclusion**

In **PostgreSQL** , the **“ALTER TABLE”** and **“ALTER COLUMN”** commands are used along with the **TYPE** Keyword to change/modify the data type of a column. These commands allow us to change/modify the type of an individual or multiple columns simultaneously. This post explained how to change the column type in **PostgreSQL** with the help of suitable examples.

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