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PL/SQL code blocks

Like any procedural language, the basic unit of PL/SQL program is a block. Within those blocks you find statements that are executed as a unit. In PL/SQL, blocks are further classified into different categories that include;

Labeled blocks - this are used to give a certain code block a name. This also makes it very easy for other people to read your code. In general, these kind of blocks allows you to refer to variables that would otherwise be invisible.

Triggers - these are blocks that are associated with events that occurs in the database. In other words, the execution of code within these blocks is triggered by an event such as insertion of data, deletion or update of data on a specific data entity or table.

Procedures and functions - also known as subprograms. These are usually stored on the database as stand-alone objects, but some prefer to store them as part of a package. To see how a procedure or function is declared in PL/SQL, please refer to our posting PL/SQL variable and block structure.

Comments - these are bocks of text that are not executed. They are purely meant to help developers understand the code. In PL/SQL, comment blocks or multi-line comments are enclosed within (/*) and (*/) symbols; where /* marks the beginning of a comment and */ marks the end of a comment. For a single line comment, you can simply use -- at the beginning of the line to let the database system know not to try to execute the statement.

For some basic blocks such as the looping constructs, IF-THEN-ELSE, you can declare one block within another. These are known as nested blocks. However you can not define a procedure within another procedure or trigger within another trigger. What you can do instead is call the procedure from another and passing along applicable values to the called procedure.

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PL/SQL code blocks

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