You can think of a package as an application. You can specify the event, whether the trigger fires before or after the event, and whether the trigger runs for each event or for each row affected by the event. Some subprograms in the packages in Table can both accept input and display output, but they cannot accept data directly from the keyboard. Data abstraction lets you work with the essential properties of data without being too involved with details. You can design a data structure first, and then design algorithms that manipulate it.
You can use the cursor to retrieve the rows of the result set one at a time. You can use cursor attributes to get information about the state of the cursor—for example, how many rows the statement has affected so far.
For more information about cursors, see "Cursors". A composite variable has internal components, which you can access individually. You can pass entire composite variables to subprograms as parameters. In a collection , the internal components are always of the same data type, and are called elements. You access each element by its unique index. Lists and arrays are classic examples of collections. In a record , the internal components can be of different data types, and are called fields.
You access each field by its name. A record variable can hold a table row, or some columns from a table row. For every column of the full or partial row, the record has a field with the same name and data type. If the structure of the row changes, then the structure of the record changes accordingly. If the declaration of the referenced item changes, then the declaration of the referencing item changes accordingly. The variables that form the data structure are called attributes.
The subprograms that manipulate the attributes are called methods. ADTs are stored in the database. ADTs let you reduce complexity by separating a large system into logical components, which you can reuse. Conditional selection statements , which let you run different statements for different data values.
For more information, see "Conditional Selection Statements". Loop statements , which let you repeat the same statements with a series of different data values. Data Structures. Operating System. Computer Network. Compiler Design. Computer Organization. Discrete Mathematics. Ethical Hacking. Computer Graphics. Software Engineering. Web Technology.
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