MYSQL

How to Create Altering tables in MySql




The format of an existing database table can be changed with an ALTER TABLEquery . This query can make a single alteration or specify as number of alterations as comma-separated list.

In the ADD COLUMN and DROP COLUMN examples the COLUMN  keyword is optional- it is what the manual calls “a pure noise word” that is only there to aid readability.

An ALTER TABLE query can ADD a complete new COLUMN to an existing table , like this :

It can also ADD a PRIMARY KEY to an existing column definition using this syntax :

An ALTER TABLE query can CHANGE the name of an existing column. The new column will not inherit any data type or modifiers specified to the original column – these must be set a new in the ALTER TABLE query, like this :

delete an entire column from the table using the DROP COLUMN keywords :

Ex :




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