Start Updating tinyint columns in oracle

Updating tinyint columns in oracle

However, as with any value participating in a UNIQUE constraint, only one null value is allowed per column.

This situation can produce unexpected results, as in the following example.

You can create a CHECK constraint with any logical (Boolean) expression that returns TRUE or FALSE based on the logical operators.

For example, the range of values for a salary column can be limited by creating a CHECK constraint that allows for only data that ranges from $15,000 through $100,000.

You can create a CHECK constraint as part of the table definition when you create a table.

If a table already exists, you can add a CHECK constraint.

For example, suppose you place a constraint on an int column My Column specifying that My Column can contain only the value 10 (My Column=10).

If you insert the value NULL into My Column, the Database Engine inserts NULL and does not return an error.

Although both a UNIQUE constraint and a PRIMARY KEY constraint enforce uniqueness, use a UNIQUE constraint instead of a PRIMARY KEY constraint when you want to enforce the uniqueness of a column, or combination of columns, that is not the primary key.