[Excerpt-database-learning] the so-called increase/decrement script when the service is upgraded __ database

Our online program upgrades always hear what incremental script, I have no idea what happened, this certification looked at the next book, finally know it;

The so-called increment script, that is, when the upgrade of a table added an element, that is, a column of data, or a table, and so on, anyway is to increase things;

table, the following SQL statement is included:

Suppose you need to add a name column to the user table:

MySQL database:

ALTER TABLE user ADD COLUMN name VARCHAR (100);

Oracle Database:

ALTER TABLE user ADD (name VARCHAR2 (100));

If you need to add more columns, such as add name, sex, old three columns in the user table:

MySQL database:

ALTER TABLE user ADD COLUMN (name VARCHAR, sex int, old INTEGER);

Oracle Database:

ALTER TABLE user ADD (name VARCHAR, sex integer, old integer);

To delete a column from a table:

Mysql/oracle Database:

ALTER TABLE user drop name;

MySQL data I personally tested found that multiple columns could not be deleted; Delete multiple columns not tested in Oracle