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Oracle alter table modify column Syntax example


Oracle Database Tips by Donald Burleson

For complete tips on Oracle alter table syntax, see the book "Easy Oracle Jumpstart".  Oracle provides "alter table" syntax to modify data columns in-place in this form:

alter table
   table_name
modify
   column_name  datatype;

If you are brave you can use a single "alter table" syntax to modify multiple columns:

alter table
   table_name
modify
   (
   column1_name  column1_datatype,
   column2_name  column2_datatype,
   column3_name  column3_datatype,
   column4_name  column4_datatype
   );

Here are some examples of Oracle "alter table" syntax to modify data columns and note that you can add constraints like NOT NULL:

ALTER TABLE
   customer
MODIFY
   (
   cust_name varchar2(100) not null,
   cust_hair_color  varchar2(20)
   )
;

We can also use Oracle "alter table" syntax in dynamic PL/SQL to modify data columns

BEGIN
SQL_STRING := 'ALTER TABLE '||:TABLE_NAME||' MODIFY '||:COLUMN_NAME||' VARCHAR2(100)';
 . . .
END;

 

 

 

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