文件名称：Sybex - Mastering Visual Basic .NET Transact SQL (VBL).pdf
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更新时间：2022-09-04 03:20:41
Sybex Mastering Visual Basic NET
Transact-SQL In Chapter 20, you builtSQL statements to retrieve and update rows in a database. You also learned all the variations of the SELECT statement. Some restrictions, however, can’t be expressed with a WHERE clause, no matter how complicated. To perform complicated searches, many programmers would rather write an application to retrieve the desired rows, process them, and then display some results. The processing could include running totals, formatting of the query’s output, calculations involving multiple rows of the same table, and so on. Most database management systems include extensions, which enhance SQL and make it behave more like a programming language. SQL Server provides a set of statements known as Transact-SQL (T-SQL). T-SQL recognizes statements that fetch rows from one or more tables, flow-control statements like IF…ELSE and WHILE, and numerous functions to manipulate strings, numeric values, and dates, similar to Visual Basic’s functions. With T-SQL you can do everything that can be done with SQL, as well as program these operations. At the very least, you can attach lengthy SQL statements to a database as stored procedures, so that you can call them by name. In addition, you can use parameters, so that the same procedure can act on different data. This chapter is an overview of T-SQL and demonstrates the basic topic with stored proce- dures that perform complicated tasks on the server. We’ll start with the COMPUTE BY state- ment, which allows you to calculate totals on groups of the rows retrieved from the database. This statement looks and feels very much like the straight SQL statements, yet it’s not part of standard SQL. Then we’ll look at T-SQL in depth. If you need to look up a function or how to declare a stored procedure’s arguments, you can use this chapter as reference material. If you’re new to T-SQL, you should read this material, because T-SQL is a powerful language, and if you’re working with or plan to switch to SQL Server, you’ll need it sooner or later. In addition, you’ll improve your Visual Basic programming. T-SQL is the native language of SQL Server. By seeing how the basic operations can be implemented in T-SQL and VB, you’ll gain a deeper under- standing of database programming.