How to change existing columns in an SQL table

How to change existing columns in an SQL table


Tables in SQL (Structured Query Language) databases may at times need to be modified. There are two approaches to do so.


An SQL development environment.


Once a connection to an SQL server is acquired and a database’s table is selected for modification, you can change its columns using two different approaches. First, you can change a column’s attributes using:

alter table tableName modify columnName columnAttributes;

Or, if you would like to change the column name as well, you may use:

alter table tableName change previousColumnName newColumnName columnAttributes;

You can use the second approach (using the keyword change) to only modify the attributes by repeating the pre-existing column name twice. This is instead of including a replacement column name after the previous column name.