The DECIMAL data type is similar to the INT data type in that when you use the number for math, it maintains precision. The difference though is obvious in the name. The DECIMAL data type allows for numbers after a decimal point (and before the decimal point). The DECIMAL data type allows us to store what is known as a fixed-point number. A fixed point number is a number that has a specific number of digits available to store numbers in. That means we can't do things like use a DECIMAL data type to store as many digits of PI as possible, because we can't store unlimited digits. We are limited to a certain number.
There are two keywords you need to understand when you are working with the DECIMAL data type, precision and scale. Precision is the number of digits and scale is the number of those digits that will come after the radix. You are going to want to provide these numbers when you declare a column of this data type.
For example, DECIMAL(5, 2) has a precision of 5 digits and a scale of 2 digits. That means we can store a maximum of two digits after the decimal and four digits total. This gives us a possible range from -999.99 to 999.99
The highest number of digits is 65, and the highest number of digits after the decimal is 30.
This data type is also known as DEC, NUMERIC, and FIXED.
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A trigger is a named PL/SQL unit that is stored in the database and executed ( fired ) in response to a specified event that occurs in the database.
Overview of Triggers.
A trigger is a named program unit that is stored in the database and fired (executed) in response to a specified event. The specified event is associated with either a table, a view, a schema, or the database, and it is one of the following:
A database manipulation (DML) statement ( DELETE , INSERT , or UPDATE )
A database definition (DDL) statement ( CREATE , ALTER , or DROP )
A database operation ( SERVERERROR , LOGON , LOGOFF , STARTUP , or SHUTDOWN )
The trigger is said to be defined on the table, view, schema, or database.
A DML trigger is fired by a DML statement, a DDL trigger is fired by a DDL statement, a DELETE trigger is fired by a DELETE statement, and so on.
An INSTEAD OF trigger is a DML trigger that is defined on a view (not a table). The database fires the INSTEAD OF trigger instead of executing the triggering DML statement. For more information, see Modifying Complex Views (INSTEAD OF Triggers).
A system trigger is defined on a schema or the database. A trigger defined on a schema fires for each event associated with the owner of the schema (the current user). A trigger defined on a database fires for each event associated with all users.
A simple trigger can fire at exactly one of the following timing points :
Before the triggering statement executes.
After the triggering statement executes.
Before each row that the triggering statement affects.
After each row that the triggering statement affects.
A compound trigger can fire at more than one timing point. Compound triggers make it easier to program an approach where you want the actions you implement for the various timing points to share common data. For more information, see Compound Triggers.