Basic SQL: Alter (Part 7)

Alter statement is used to alter the structure of database objects, and like Create statement, different objects have different syntax. Below are example to alter a table:

1. Add column:
alter table [table name]
add [column name] [data type]

   Example:
alter table temp
add test varchar(10);


2. Remove column:
alter table [table name]
drop column [column name]

   Example:
alter table temp
drop column test;


3. Add constraint:
alter table [table name]
add constraint [constraint name] [constraint type] [constraint details]

   Example:
alter table temp
add constraint temp_uk unique (name);


4. Remove constraint:
alter table [table name]
drop constraint [constraint name]

   Example:
alter table temp
drop constraint temp_uk;

   

To change password of a user, use syntax below:
alter user [user name]
identified by [new password]

Example:
alter user james
identified by new_password;