Database Reference
In-Depth Information
Some Limitations of SQL
As can be seen from Chapters 11 - 14, SQL is a very powerful programming language,
ideally suited for the management of databases. However, like all languages, SQL
has limitations. This chapter briefly examines some of these limitations. The chapter
proceeds as follows:
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Programming Limitations
•
Limitations on Views
•
Foreign Key Constraint Specification
•
Superfluous Enforcement of Referential Integrity
•
Limitations on Calculated Columns
•
If-Then Limitation
•
Summary and Concluding Remarks
15.1 Programming Limitations
While SQL is a very sophisticated fourth generation language (4GL) for database
management, it does not have many facilities that are normally present in a traditional
high-level language (HLL). These include user interface programming and traditional
internal processing facilities for basic data structures. The truth is, SQL was never
intended for these facilities. SQL is therefore most effective in an environment where it
is embedded in HLL code. The HLL may be the host language of a DBMS, or some other
language that the DBMS supports.
Quite often, in complex software development projects, the developer will encounter
situations where a single SQL statement is inadequate to service the needs of the user.
What is required is a series of SQL statements (and possibly non-SQL statements). The
limitations on logical views (discussed in the following section) provide a case in point.
Again, an HLL support is often a perfect antidote for these scenarios.
15.2 Limitations on Views
The limitations on logical views were mentioned in Chapter 13 (sections 13.1 and 13.2),
without much elaboration. Let us revisit this matter here.
