SQL data manipulation language
…the language of the Zen teacher reveals ideas rather than feelings and intentions. And therefore it plays quite a different role, as compared to the casual use of the language; as the choice of words is up to the teacher, and it works miracles in the sphere of its traditional employment, and the disciple discovers his own self, conceives himself, and thus the casual phrase becomes the key to the idea.
Hopscotch, Julio Cortazar.
This book is devoted to practical use of SQL(Structured Query Language) is a database computer language designed for the retrieval and management of data in relational database management systems (RDBMS), database schema creation and modification, and database object access control management.SQL language, i. e. primarily to the use of SELECT statement, retrieving the data from relational database, and INSERT, UPDATE and DELETE statements, that are used for data modification. These statements make up the SQL sublanguage, which is also called Data Manipulation Language (or DML). In this «theoretical» chapter we try to focus on those syntactic constructions of the statements in question, which in the first place are in complete correspondence with SQL-92 Standard, and in the second place, are supported by practically all the commercial DBMS. It is quite clear that we also cannot ignore some of the peculiarities of their execution. It can be explained by the fact that the extensions of the Standard presupposed for each implementation quite often enable us to write a query in the more concise way, and also by the fact that some of the cases are not covered by standard and, as a rule, are determined on implementation level. As the site is devoted to MS Cистема управления реляционными базами данных (СУБД), разработанная корпорацией Microsoft.SQL Server 2005, the peculiarities of the implementation, which are stipulated specially, mostly refer to this particular product. When the possibility arises of doing exercises on other DBMS, this section about diversities of their implementation will be extended. In particular, this is true about the functions of string processing and the values like date/time, which are considered in Chapter 7 (Part III). It is worth mentioning, that practically all the tasks considered here and constituting the first step of the testing procedure on the site, can be completed using only standard means. It can be proved by numerous visitors of the site, who in their work use various DBMS from FoxPro to Oracle.
Description of the syntax of operators of the language is substantiated with examples of the queries that address training database, brief description of which is provided in Appendix*1. Besides, many paragraphs are supplied with the list of exercises, recommended for solution of the problems intended for revising the corresponding material. The texts of the problems, that constitute the initial step of the testing procedure on the site and some of which are analyzed in the book, are given in Appendix*2.
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