The execution of the above query statement gives the following output: For this, we can make the use of the following query statement that follows the first syntax – ALTER TABLE customer_detailsĪDD COLUMN last_purchased_at TIMESTAMP WITH TIME ZONE NOT NULL Consider that we want to add the column named last purchased on with TIMESTAMP datatype. We can even add a single column by making the use of first syntax. For this, we can make the use of the following query statement to add these two columns to our existing table customer_details – ALTER TABLE customer_details Suppose that we want to add the columns named birth_date and anniversary_date having the DATE datatype and NOT NULL constraint over them so that the column will not store NULL value in it. The execution of the above query statement gives the following output – Let us try to create one table named customer_details for storing customer data and demonstrating the use of ALTER TABLE ADD COLUMN command using the below query statement – CREATE TABLE customer_details Note: If you will try to insert a column that already exists in the table then the query statement of adding the column will issue an error. For example, you can specify the NOT NULL constraint so that the column will never accept NULLL values for storing inside it or you can specify constraint as GENERATED BY DEFAULT AS IDENTITY for the column whose value will be auto-generated internally one by one which is mostly done for columns behaving as primary keys.
constraints if any – You can specify any kind of restrictions that you want to apply on the column you are adding.Most common datatypes used in PL/ SQL areVARCHAR2, NUMBER, TIMESTAMP, DATE, etc. datatype of the column – This will be the datatype of the corresponding column of the table specifying the type of value that will be stored in the respective column.Name of column1, Name of column2, … – While adding multiple columns to the existing table, you should specify the column names which are unique and which do not already exist in the table in which you are trying to add them.Name of column – When you are trying to add a single column this should be specified for the name of the column that you wish to add to the table.If the table with the specified name does not exist the command will throw an error saying No Table with such name exists in the database. Name of table – This should be the name of the existing table in which you wish to add a new column in PL/ SQL. In both of the above-mentioned syntaxes, the terminologies used are as explained here one by one – "Name of column2" "datatype of the column" "constraints if any", ("Name of column1" "datatype of the column" "constraints if any",
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