Introduction to SQL Standards

Press: This is based on a few essays I wrote a long long ago to reorganize.

　　 SQLis aStructured Query Languagethe acronym, which was formerly known as the Relational database prototype systemSystem RThe use ofSEQUELlanguage. As a standard language for accessing relational databases,SQLhas been widely used since its inception , not only the famous large-scale commercial database productsOracle,DB2,Sybase,SQL Serversupport It, many open-source database products such asPostgreSQL,MySQLalso support it, even some small products such asAccessalso supportsSQL. In recent years the boomingNoSQLThe system was originally declared no longer neededSQLand later had to be amended toNot only SQL, to HugSQL.

Blue giant IBM for relational databases and SQL The Formation and normalization of language has had a significant impact on the first version of the SQL Standard SQL86 is based on System R Manual. Unfortunately IBM didn't have a product idea at first, but Oracle pioneered the 1979 year in support Commercial products for SQL. With the development of database technology and application, it is a realistic need to provide a consistent language for various relational database systems.

　　 theSQLThe institutions most affected by the standards are naturally those of well-known database producers, while the specific ones are non-profit organizations such as the International Organization for StandardizationISO, American National Standards CommitteeANSIand so on. Countries will usually followISOStandards andANSIstandards (many of the standards of the two institutions are almost equal) to develop their own national standards. China isISOThe Member States of the standard Committee also regularly translate the Chinese version of some international standards. Standards in order to avoid the use of specific product terminology, often abstract a lot of nouns, thus increasing the difficulty of reading and understanding, translated into Chinese after more easily lied. For database system implementation and users, many times it is better to read the English version directly. Although the official standard is not likeRFCthat can be freely available on the web, and the draft standard is relatively easy to find (for example:http://www.jtc1sc32.org/doc/). There is no substantial difference between the draft standards to be approved and the final standards, which can meet the needs of daily work.

　　 Below isSQLBrief History of the development:
1986years,ANSI x3.135-1986,ISO/IEC 9075:1986,SQL-86
1989years,ANSI x3.135-1989,ISO/IEC 9075:1989,SQL-89
1992years,ANSI x3.135-1992,ISO/IEC 9075:1992,SQL-92(SQL2)
1999years,ISO/IEC 9075:1999,sql:1999(SQL3)
2003years,ISO/IEC 9075:2003,sql:2003
-years,ISO/IEC 9075:2008,sql:2008
.years,ISO/IEC 9075:2011,sql:2011

Careful reader can find, from the sql:1999 start, the dash in the standard abbreviation ( - : iso standard customary with colons, ansi 2000 year issue.

SQL86 about dozens of pages, sql92 The body has about 500 page, and sql99 1000 page. As you can see, from the sql99 start, sql the size of the standard is very large, the content is all-encompassing, no one has been able to master all the content of the standard. With sql:2003 9 parts (the intermediate number vacancy is the one that was once occupied and then discarded):

iso/iec9075-1: Framework (sql/framework)
ISO/IEC 9075-2: Foundation (sql/foundation)
ISO/IEC 9075-3: Call level Interface (SQL/CLI)
ISO/IEC 9075-4: Persistent Stored Modules (SQL/PSM)
ISO/IEC 9075 -9:management of External Data (sql/med)
ISO/IEC 9075-10:object Language Bindings (sql/olb)
ISO/IEC 9075-11:infor Mation and Definition Schemas (sql/schemata)
ISO/IEC 9075-13:java Routines and Types Using the Java programming Langua GE (SQL/JRT)
ISO/IEC 9075-14:xml-related Specifications (Sql/xml)

      The specific work is done by iso iec co-founded a technical committee jtc1/sc32 sql3 The period is long and there is a lot of controversy during the formulation period. For example, the article " is SQL a Real standard anymore? sql The standardization process was questioned.

If you want to understand the standard content, the more recommended method is extensive reading 　　 SQL92 (because it deals with SQL The most basic and core content), and then incrementally read other standards. Every time the standard is updated, the members of the Committee provide a good introduction document for everyone. For example, for the latest sql:2011,sigmodrecord has a very good introduction:http://www.sigmod.org/ Publications/sigmod-record/1203/pdfs/10.industry.zemke.pdf

and finally, a brief introduction 　　 SQLthe degree of compliance with the standard. Most people mentionSQLStandard, the content involved is actuallySQL92The most basic or central part of it. SQL92are hierarchical in nature, including entry-level, excessive, intermediate, and full-scale. To verify the compliance of the specific product to the standard,NISTa project has also been launched specifically to make a test set of standard conformance:Http://itl.nist.gov/div897/ctg/sql_form.htm. However,SQLThe standard contains a lot of content, and there are many features to the newSQLproducts are becoming less important. FromSQL99after that, the definition of compliance in the standard is no longer graded, but is changed to core compatibility and feature compatibility, and there is no agency to launch authoritativeSQLTest certification of the standard compliance level.

Introduction to SQL Standards