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Custom Data Types
- PL SQL is a strongly typed language. For every variable used in a program or subprogram, the variable must be declared with a data type. PL SQL comes with some data types already defined.
- Scalars are atomic data types such as NUMBER, BOOLEAN, VARCHAR, and many more while composite data types consist of one or more scalars. Examples of composite data types are record types, collection types, and object types.
- Subtypes do not introduce a new type. They, however, place optional constraints on a base type. They generally improve the readability and reliability of the code.
- Composite data types can take 3 forms which are record types, object types, and collection types. Internal components in the composite data type could either be a scalar or another composite data type. Internal components can be accessed using a dot notation.
- Object types can have 3 components which are attributes, name, and methods. Method keywords could be preceded with STATIC or COMPARISON. Object types may require a body like packages in PL/SQL if the object has methods.
- There are 3 types of collections which are associative arrays, variable-sized arrays (VARRAYS), and nested tables.
- Subtypes, records, and collections are usually not preceded with the CREATE keyword when declared. They are used and declared in packages and subprograms.
- Custom data types could be instrumental in making your code more optimal, better performing, and readable.
- Live SQL platform can be used to practice these concepts.
- Custom data types in PL SQL are Scalar and Composite data types. Scalar categories can be further constrained using Subtypes. Composite data types are user-defined types made from one or more scalar data types. They are created by a user, and allow us to create abstractions of real-world objects, similar to other object-oriented programming languages. The three educational pieces to composite types in PL/SQL are nested tables,(varrays) variable sized arrays, and associative arrays.
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