Making changes in a table

Question

I have two tables. one of the table has a primary key which corresponds to foreign key in another table. now i have to change data in first table in a column which acts as primary key . How can i go about changing data in primary column.
Thanks

Answer 1

Hi,
Say the primary_key = 101 in table_a, and foreign_key = 101 in table_b. One way to change the 101 to 102 is:
(1) Add a new row to table_a, with primary_key=102
INSERT INTO table_a (primary_key, col_2, col_3, ...)
     SELECT           102,        col_2, col_3, ...
     FROM           table_a
     WHERE           primary_key = 101;(2) Change any existing rows in table_b to reference this new row in table_a"
{code}
UPDATE     table_b
SET     foreign_key     = 102
WHERE     foreign_key     = 101;
{code}
(3) Remove the old row from table_a
{code}
DELETE     table_a
WHERE     primary_key     = 101;
{code}
But, as Whitehat said, changing prmary keys is a bad way to design tables. A lot of folks use +Surrogate Keys+ that have no meaining except as keys. Since they don;t mean anything in the real application, your real applcation will never have any reason to change them.