How to add same column to multiple tables in a DB and fill it with a constant value?

I have a database with multiple tables. I want to add a new column to each one of them and fill these column 开发者_JAVA百科with some constant integer value. My search on google did not give me desired answer.

I am using PostgreSQL and PHP.

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Can't you use ALTER TABLE to create a new column and SET DEFAULT to set the default value to all column fields?

Like:

ALTER TABLE mytable ADD COLUMN mynumber integer; ALTER mynumber SET DEFAULT 7

(http://www.postgresql.org/docs/8.2/static/sql-altertable.html)