- PL/SQL Tutorial
- Pl Sql Insert And Reference Key Generated Always Lyrics
- Pl Sql Insert And Reference Key Generated Always Lyrics
- PL/SQL Useful Resources
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This page describes how to use the Application Express Interactive Grid component - even without a table. Displayed data is being generated and end user input are being processed with PL/SQL. Virtual columns and 11g partitioning. However, the concept of virtual columns has the nice side effect of assisting in streamlining partitioning. For example, assume that we have a table that is partitioned by year-month (i.e. With 11g virtual columns, we can simply compute the partition key virtually, using a DATE column.
- Summary: in this tutorial, you will learn about Oracle virtual columns and how to use them in your database tables. Introduction to the Oracle virtual column. A virtual column is a table column whose values are calculated automatically using other column values, or another deterministic expression.
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In this chapter, we will discuss Variables in Pl/SQL. A variable is nothing but a name given to a storage area that our programs can manipulate. Each variable in PL/SQL has a specific data type, which determines the size and the layout of the variable's memory; the range of values that can be stored within that memory and the set of operations that can be applied to the variable.
The name of a PL/SQL variable consists of a letter optionally followed by more letters, numerals, dollar signs, underscores, and number signs and should not exceed 30 characters. By default, variable names are not case-sensitive. You cannot use a reserved PL/SQL keyword as a variable name.
PL/SQL programming language allows to define various types of variables, such as date time data types, records, collections, etc. which we will cover in subsequent chapters. For this chapter, let us study only basic variable types.
Variable Declaration in PL/SQL
PL/SQL variables must be declared in the declaration section or in a package as a global variable. When you declare a variable, PL/SQL allocates memory for the variable's value and the storage location is identified by the variable name.
The syntax for declaring a variable is −
Where, variable_name is a valid identifier in PL/SQL, datatype must be a valid PL/SQL data type or any user defined data type which we already have discussed in the last chapter. Some valid variable declarations along with their definition are shown below −
When you provide a size, scale or precision limit with the data type, it is called a constrained declaration. Constrained declarations require less memory than unconstrained declarations. For example −
![Insert Insert](/uploads/1/2/6/2/126264636/440012900.jpg)
![Pl sql insert and reference key generated always online Pl sql insert and reference key generated always online](/uploads/1/2/6/2/126264636/597174679.png)
Initializing Variables in PL/SQL
Whenever you declare a variable, PL/SQL assigns it a default value of NULL. If you want to initialize a variable with a value other than the NULL value, you can do so during the declaration, using either of the following −
- The DEFAULT keyword
- The assignment operator
For example −
You can also specify that a variable should not have a NULL value using the NOT NULL constraint. If you use the NOT NULL constraint, you must explicitly assign an initial value for that variable.
It is a good programming practice to initialize variables properly otherwise, sometimes programs would produce unexpected results. Try the following example which makes use of various types of variables −
When the above code is executed, it produces the following result −
Variable Scope in PL/SQL
PL/SQL allows the nesting of blocks, i.e., each program block may contain another inner block. If a variable is declared within an inner block, it is not accessible to the outer block. However, if a variable is declared and accessible to an outer block, it is also accessible to all nested inner blocks. There are two types of variable scope −
- Local variables − Variables declared in an inner block and not accessible to outer blocks.
- Global variables − Variables declared in the outermost block or a package.
Following example shows the usage of Local and Global variables in its simple form −
When the above code is executed, it produces the following result −
Pl Sql Insert And Reference Key Generated Always Lyrics
Assigning SQL Query Results to PL/SQL Variables
You can use the SELECT INTO statement of SQL to assign values to PL/SQL variables. For each item in the SELECT list, there must be a corresponding, type-compatible variable in the INTO list. The following example illustrates the concept. Let us create a table named CUSTOMERS −
(For SQL statements, please refer to the SQL tutorial)
Let us now insert some values in the table −
The following program assigns values from the above table to PL/SQL variables using the SELECT INTO clause of SQL − How are session keys generated.
Pl Sql Insert And Reference Key Generated Always Lyrics
When the above code is executed, it produces the following result −
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