The PostgreSQL PL/pgSQL control statements

The PostgreSQL control structure is an essential part of the PL/pgSQL language; it enables developers to code very complex business logic inside PostgreSQL.

Declaration statements

The general syntax of a variable declaration is as follows:

name [ CONSTANT ] type [ COLLATE collation_name ] [ NOT NULL ] [ { DEFAULT | := | = } expression ];

Let's see what the keywords mean:

• name: The name should follow the naming rules discussed in Chapter 3, PostgreSQL Basic Building Blocks. For example, the name should not start with an integer.

• CONSTANT: The variable cannot be assigned another value after the initialization. This is useful in defining constant variables such as Pi.

• type: The type of variable can be simple such as integer, user defined data type, pseudo type, record, and so on. Since a type is created implicitly on creating a table, one can use this type to declare a variable.

  Tip

  In PostgreSQL, the following two declarations are equivalent; however...