Introduction to SQL Standards
This chapter compares important SQL standards.
SQL applications can be written in a vendor independent manner by using only those parts of SQL which are defined in one or more standards. This makes it possible to move applications between different database systems without the need to rewrite a substantial amount of code.
Mimer's policy is to develop Mimer SQL as far as possible in accordance with the established standards. This enables users to switch to and from Mimer SQL easily.
The following SQL standards are discussed in this manual:
- X/Open SQL 1995 - referred to here as X/Open-95
- ISO/IEC 9075: - referred to here as SQL92
- SQL/PSM - the section of the SQL92 standard covering Persistent Stored Modules.
SQL92 has been developed by ANSI/ISO. This standard is written in a very formal manner. It is therefore difficult to use as a programming guide.
Different standards vary in the detail of their specifications. While any one standard defines a workable version of SQL, there are few, if any, vendors who supply database management systems with a specification that falls entirely within the bounds of a single standard.
Mimer SQL combines many of the advantages of the different standards.
The following sections describe the SQL standards in more detail.
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