Skip to main content

Posts

Showing posts with the label what are the column option used in mysql

Column Options

A table must have at least one column. Each column has to have a name and a data type. And there are several options for column data that can be used as part of the table creation command. These options modify how MySQL handles the associated column. Such  as the following; NULL   Allows values stored as  NULL   The default option NOT NULL Disallows NULL  values  Saves response time and in some cases disk space  A necessity for a  PRIMARY KEY DEFAULT    If no value is specified by the user at insertion of new data, this data will be stored in the field AUTO_INCREMENT  Only works for Integer data type columns Automatically generates a unique, positive number sequence for each row in a table (for UNIQUE or PRIMARY KEY  columns)  Using NULL will insert the next available number instead   Not specifying a value for the column will also work  Cannot exceed the upper limit of the  specific data type (i.e. 255 for a  TINYINT)   If rows are deleted containing valu